When the world was made there were leftover bits. These shell fragments from previous creation or cosmic crumbs or pocket worlds make up most of the strange lands you can visit. These fragments were occupied by various factions which changed over aeons. These planes were colonised and fought over by early powers and many contain remnants of then. Faerie and Demons occupy the most. Other fragments were linked and made as extensions to the world by adding extra hells and heavens which can only be accessed in order.
Later ages when gods left after creation, trolls mostly a spent force, giant scattered and their control over the cosmos was lost mostly to faerie folk. After an age of evil that kept the gods at bay humans, demihumans, goblinoids and orcs have been the thriving peoples of the age. Mortals have not interacted with these planar fragments of the old order or petty domains of rebel servants of the gods.
Most plane travel is through universal points like using the sea to go to underwater fairyland or a forest fairy ring or a cave at the right time and the right place. At least your first planar trips use these. Each Planeshift wizard spell includes one planar location described in detail. Some of these are tricks spread by imps or cultists. Some have samples of soil from another plane they can use to home in on but once again - who gave these samples to you? ESP on a planar being might help.
Who Colonised this World?
The first d4 predate the creation, d8 elemental building blocks of the world made, d10 dragons birthed titans who rebelled d12 gods rebelled from titans and made their own servitor spirits d16 gods fought each other and servitors split into factions and world made from dead titans and giants and the leftovers became fragments to feud over, devils built hell to torment the damned and imprison the dead, demons grabbed petty territories to shape to their own pleasure, various heavens were built culminating in a multiplanar celestial citadel the cosmos is administered from. d20 Includes mortal born descendants of titans (giants and trolls) and servitors of the gods who steward the natural world. The dice roll is some keywords for factional differences. The number rolled here don't represent all these as equally successful - currently, demons and faeries have occupied many such planes while giants have lost ground. You could roll a d3 of these for past occupants and a new arrival on the Recent planar explorers table. This helps you populate a world with inhabitants and ruins.
d20 Pocket Planar Colonisers
Who got here first? Roll a d3 times for different arrivals or
1 Dark d4 1=Void 2=Shadows 3=Nightmares 4=Death
2 Light d4 1=Source 2=Fullness 3=Dreamlands 4=Life
3 Chaos d4 1=Primal 2=Entropy 3=Disorder 4=Vortex
4 Law d4 1=Stasis 2=Transcentral 3=Eternity 4=Cosmos
5 Fire d4 1=Radience 2=Volcanic 3=Heat 4=Ash
6 Earth d4 1=Rock 2=Crystal 3=Metal 4=Wood
7 Air d4 1=Cloud 2=Storm 3=Cold 4=Sky
8 Water d4 1=Ice 2= 3=Salt 4=Slime
9 Dragons d4 1=Sea (Tiamat) 2=Earth 3=Heaven 4=Underworld (Nidhogg)
10 Titans d4 1=Earth 2=Sea 3=Sky 4=Death
11 Gods d6 1=Earth 2=Solar 3=Sky 4=Moon 5=Underworld 6=Evil
12 Spirits d6 1=Ancestors 2=Land 3=Water 4=Animal 5=Plant 6=Dead
13 Daemons d4 1=Earth 2=Darkness 3=Death 4=Void
14 Angels d4 1=Light 2=Fire 3=Holy 4=Heavenly
15 Demons d4 1=Plague 2=Darkness 3=Chaos 4=Elder
16 Devils d4 1=Fire 2=Ice 3=Tormentors 4=Hell's Army
17 Sylvian d4 1=Nymphs 2=Beast folk 3=Tree folk 4=Hybrid beast folk
18 Faeries d4 1=Sprites & brownies 2=Elves 3=Goblins 4=Faerie Court (d2 1=bright 2=dark)
19 Giants d4 1=Ice 2=Fire 3=Sky 4=Chaos Mutant Formarians
20 Trolls d4 1=Cave 2=Arcane(magicians) 3=Chaos 4=Mountain
d12 Recent Planar Explorers
These are most likely to have occupied in historical times or even recently
1 Elves d4 1=Pine 2=Sky 3=Celestial 4=Astral (Psionic)
2 Dwarves d4 1=Mountain 2=Underland 3=Fortress 4=Darkness
3 Halflings d4 1=Adventurers 2=Colonists 3=Hedonists 4=Faerie
4 Gnomes d4 1=Underland 2=Darkness 3=Woodland 4=Cannibal
5 Goblinoids d4 1=Darkness 2=Chaos 3=Nature 4=Faerie
6 Orcs d4 1=Barbarian 2=Mercenary 3=Hell spawn 4=Wizard Thralls
7 Beastfolk d4 1=Tribal 2=Smaller Beastlings 3=Monster Empire 4=Wizard Thralls
8 Humanoids d4 1=Elemental Abhumans 2=Spiritfolk 3=Demons 4=Undead
9 Human magicians d4 1=Wzard 2=Priest 3=Druid 4=Sorcerer
10 Human outcastes d4 1=Prison 2=Damned 3=Cursed 4=Monastary
11 Human adventurers d4 1=Invaders 2=Colonists 3=Stranded 4=Heroes
12 Human cult d4 1=Cloud 2=Storm 3=Old Ones 4=Demons
Arrival
In my game, Planeshift like Teleport requires well-known target location preferably one you have been to or can see. You can research a place like the palace of efreeti princes on the plane of fire in a book and go blind but you never met anyone who did this. You can hear of a reputed gateway from some kind of record or expert. Following their advice use plane shift using extra conditions on this table as prescribed and can gate to a prescribed planar location set by the particular gate. Once you get to another plane you can go back and forth to places you know on the mortal world or other planes you have visited.
d12 Research - Who knows how to reach this universe?
How do you find accurate directions to a plane you never been to before?
1 On books in the college of magic library planar lore collection
2 Inscribed on worn stones in a forgotten language
3 A magician-scholar who has become a hermit
4 Recorded in temple archives but restricted access to outsiders
5 A demi-human clan leader who is a notorious grump
6 A dragon witnessed the gate in use several times and knows
7 A lost book in a sprawling library or ruined archive
8 An aged hero used this gate in the past and spent years on the other side
9 A witch or hag in a cave or shack knows but is a bit scary
10 A being knows but it wants something d4 1=spirit 2=demihuman 3=demon 4=devil
11 Records of a noble have secret but is hidden in estate
12 A book of the way by a traveller was carried away by monsters
d12 Gates - Where do you find them?
Where do you find gateways?
1 Through the branches or roots of the cosmic world tree or a tree manifestation
2 Through ancient stone passages in deep underland chasms
3 Imbibing a special herb or mushroom lets your spirit pass through planar membrane
4 Through another dimension you have to reach first
5 Place of natural spectacle or wonder or a simple fairie ring
6 Well or pond, well, waterfall, place in the sea, grotto pool
7 A stone arch in a ruin in a faraway wilderness used by ancients
8 In the cosmic ocean reachable by sailing secret routes under the right stars
9 Strange storm, wind or fog sweeps people up to otherworld at certain times and places
10 A volcanic vent or bubbling grotto or geyser
11 Through reaching celestial objects in the sky at night like stars and planets
12 A magical hidden door deep in a dungeon of the ancients
d12 Gate Conditions - How do you pass the gate?
What does the gate require to open?
1 Star must be right in the sky making access seasonal
2 Enter a trance and your dream self passes the barrier
3 Requires an object to act as a key 1in4 requires a unique thing
4 Requires drug abuse d4 1=alcohol 2=black lotus 3=opium 4=mushrooms
5 Must answer the riddle of the guardian
6 Must battle or overcome the guardian
7 Must personally satisfy the guardian you are worthy
8 Requires living sacrifice d4 1=virgin 2=oxen 3=criminal 4=dragon or other monster
9 Requires a ritual or ceremony with chanting and novelty costumes
10 Requires living sacrifice d4 1=virgin 2=oxen 3=criminal 4=burn valuables
11 Sound of a magic instrument or rare creature
12 Must summon a specific planar being by name to open the gate
d12 Size - How Extensive is World?
Can range from a room to feels as big as the mortal world
1 All inside a house or small building or cave but bigger on the inside2 All inside a house or castle or estate
3 A mile across kingdom or island or valley or cavern or forest
4 Hours travel across, possibly a village or island
5 Day travel across, a small kingdom or land
6 Week travel across, a modest kingdom and wilderness
7 Month travel across, multiple kingdoms or one huge one and wilderness
8 Season travel across, multiple kingdoms or one huge one and wilderness
9 Year travel across, multiple kingdoms and several great empires
10 World is linked serially of d6+1 planes of size d6 on this table
11 World is a Mobius strip and folds in on self-giving the appearance of being infinite plane
12 World is Tesseract and folds in on self infinitely with a d6+1 distinct worlds within hidden from everyday view but accessible via shortcuts at certain angles, reflective surfaces and other means, strange geometric beings of law come to fix or hide cosmic incongruities
d12 Interplanar Travel - What is In between Worlds?
Usually, a spell using one of these protects the user from local effects
1 Branches, roots and passages of the cosmic world tree you climb through
2 Waters of the cosmic world ocean you can sail or swim through
3 Void, unnatural darkness with horrible elder beings lurking here kept away with light
4 Tunnels in mines or caves, a network within the cosmic mountain of the cosmos
5 Cosmic fire with vast cosmic explosions and streams of superheated matter
6 Dream lands can be accessed similar to astral form in sleep or physical form
7 Nightmare lands accessed similar to astral form in sleep or physical form
8 Eternal Sky accessible on high mountain tops or into upper air and cloud kingdoms
9 Fleshy tunnels within a living world of meat known as Xor
10 Dungeon Dimension a self-aware malicious eternal monster-filled labyrinth
11 The Mists swallow travellers, leaving them somewhere else directed by some curse
12 Wood Between Worlds a fairy forest with pools, fairy rings and stone circle gates
d100 Recent Planar Problems
1 Some ancient being arises to terrify occupants
2 Ancient ruins here hold secrets of the ancients and terrible wars
3 A hostile planar force has been raiding and invading
4 A new monster species has been causing trouble
5 A powerful being and minions arrived and built a fearsome stronghold
6 Plane has merged with another plane and the collision is catastrophic
7 Some fugitive has come here and is pursued by supernatural beings
8 Spies of another plane are working to annex this world
9 The ruler of the plane has changed d4 1=sadism 2=xenophobe 3=greedy 4=warmonger
10 Rulership struggle d4 1=civil war 2=revolution 3=guerilla army 4=leadership crisis
11 A strange monolith has been bringing new strange beings here
12 A relic or great machine has been found attracting enemies and struggles for power
13 A terrible apocalypse struck mostly destroying a civilisation
14 A terrible dungeon or strange fortress here has menaced the realm for aeons 15 A god or monster demands a terrible tithe from local thralls
16 A great beast of godling is buried here and trouble makers risk opening
17 Temple has a special connection to a deity and keeps some important relic
18 Another plane is going to impact this one and locals worried
19 Plane is moving from its ordained cosmic alignment and something buried in deep is responsible
20 A cult are aiding demons invasion plans
20 A hidden civilisation is causing problems with the planar orbit
21 An elemental power node has appeared or been found with an elemental guardian
22 The plane is waged in a long and ancient war covered in ruins and battle damage
23 The plane prone to mysterious weather they attribute to some enemy power
24 Giant bugs have been appearing d4 1=ants 2=spiders 3=scorpions 4=locusts, the bugs are tainted with some other planar power and part of a prelude to invasion
25 Doppelganger spies and saboteurs flood the land serving some enemy
26 Imps constantly offering people petty magic items in deals for souls
27 An undead horror has been growing and a lord of terror has a secret lair
28 A planar prison has been found from long ago holds some being who offers knowledge and power to any that free it
29 Some ancient evil is entombed in a tomb and its cultists from across planes keep coming
30 Elemental storms appearing causing problems and locals fear annihilation
31 A prophet has declared the world is doomed and people in a panic
32 Adventurers have found the helm of a small plane and are dangerously disrupting the harmony of the spheres on their wreckless travells
33 Plane has become snagged in a branch of the world tree inviting travel both ways
34 Plane has waters become atuned to world ocean and planar flotsam and jetsam turn up on shore
35 Strange beings have been entering world from bodies of water
36 Strange lights in the sky indicate intruders from the void have been creeping into the world
37 Strange vessel or star fell with a blast, locals concerned
38 Member of rulers household corrupted by a dark power
39 Magician has been probing the depths to learn secret lore of the old dead gods and dragons making up planar material
40 Locals have had outbreaks of people showing traits of long gone progenitors, the most affected have fled to old caves and ruins
41 A ruined gate was activated and opened a network long fallen to chaos demons
42 A vampire cult have been spreading influence and desire to rule to commoner cattle, some are helping vampires seeking immortality
43 A population have built on top of a titan or great monster corpse and locals exploiting it, locals have begun worshipping the beast and going to resurrect it
44 Quakes over the land have the high council worries, adventurers wanted to take control of the planes hidden helm temple deep in the earth
45 Someone plans to land the plane somewhere on the mortal world possibly as an island or isolated valley
46 A locked gate was found in a dungeon, entrance to a prison pocket dimension within this plane to hide it from inhabitants allies. Some local faction think releasing the prisoners a good idea
47 Long ago demons here were petrified and worshipped as monoliths for aeons. A wizard came and freed one now more evil pilgrims are visiting to free the demons
48 Other stars in the night sky are gates in the dome of the sky to other worlds, a criminal wizard recently stone some relics and fled through one in a constellation
49 Can see other d6 small planes floating in the sky in the distance accessible by flight, they recently were caught in this worlds mass
50 Cupboards and doors here frequently open into other dimensions and the problem is growing
51 A wizard has built a tower and has hijacked the helm of the plane for some bad reason
52 Someone has found a stone pit with something inside promising wishes if freed
53 Local rich have been signing pacts to hell and are being more systemically cruel than normal instituting new taxes and obligations but free blood sports and a few beers
54 Cursed magic items are flooding market, many shift alignment
55 A great swarm of dragons have come here to nest, hungry dragons will case famine and loss of life
56 Mutations have become more common and mutant scum kept away by prejudice are showing their god-awful faces in public!
57 A zealous sect of paladins have come and ar judging and killing all they meet by rediculous standards of planar beings. They have a fort and some locals joining their mad crusade
58 A great festival is almost ready but some naughty person has taken that special thing/mascot/person they need and is missing
59 By night creatures have been attacking and strange mists have increased
60 An angel come to judge the wicked and aid the needy, people are surprised by its harsh judgements but plenty get gifts of gold and magic and healing
61 Someone has taken all the kingdoms supply of d4 1=gold 2=food 3=children 4=wine
62 Powerful divine being has appeared demanding sacrifices and souls tribute
63 A mysterious benevolent foreigner from somewhere never seen before offers an allegiance contract and offer gifts for all in the land (d4 1=demon lord 2=devil noble 3=angel of death 4=lich)
64 Creatures from the dreamlands have been pouring in
65 Beings from nightmare lands have been infiltrating
66 Devil has come granting wishes for soul deals never to be repeated
67 Demon has come to ally with the ruler's enemies
68 A terrible plague is being spread by chaos cultists, beast folk and demons
69 Lycanthropy is breaking out across the land and is a dangerous cult
70 A great dragon has come to plunder food and wealth and build a new lair
71 A clan of giants have arrived and believe they are rulers and locals just animals
72 A necromancer has been building an army of the dead
73 Giant fungus has bee overgrowing land
74 Giant trees and forests are overgrowing land
75 Giant flying pyramid or ziggurat landed recently
76 Strangers from another world have been causing problems here angering mobs
77 Magical monsters have made large areas difficult for humans
78 Giant burrowing monsters have been eliminating locals and nobody has seen one
79 Pesky elves or faeries in the wilderness play cruel tricks on residents
80 Some unknown race is living underneath the land and by night they creep out
81 Witches and fear of witches has gone wild stirring mobs to violence
82 Strange ruin discoveries have locals prying into past secrets best forgotten
83 Petty gods are visiting here often for some reason, weird magic freaks everywhere
84 A god has come with servants to visit stirring local religions
85 Archons of law have come to annex this world for raw materials in the repair of the cosmos
86 A chaos rift releases slimes and spawn and mutant cultist swallowed up long ago
87 A great ruined engine is discovered from ruined ancient outpost from when gods waged war, the damaged device is greatly desired by a d3 cosmic factions
88 A cult have been calling forth things from the outer darkness from beyond and people dont like it
89 A warband of chaos demon mercenaries arrive for some rest and recreation and ruination
90 A demon prince has been spreading news thy will be ruler soon, banners, graffiti, printed pamphlets and dreams have been alarming population in fear, many tempting to start demon worship now to be spared
91 Strange new carnivorous plants have been spreading
92 Popular new religion stirring up trouble
93 Huge flying being arrives to rest, ridden by people to travel between worlds
94 Giants claiming to serve long-dead evil titan demand tribute and sacrifices
95 A cult calling on the old ones have called things from beyond to lurch and flail across this world
96 Elves construct a citadel here so they may come as they please alarming locals
97 Locals have survived a terrible war and still rebuilding and repairing lives
98 Dungeons that never existed before have sprung up, intrusions from the
99 Faeriefolk are replacing babies in an all-out secret colonisation scheme
100 Two cosmic beings or factions declare this realm will be there's, both invade and trash the place, possibly one side less terrible