Outer Planes Timeline

Key events and eras that shape the Great Wheel’s Outer Planes—from belief-forged beginnings to modern planar politics.

Year	Event
Before Time	The concept of alignment and belief coalesce into proto-planes; moral/ethical "directions" exist before maps do.
Mythic Age	The Outer Planes stabilize into a ring of afterlives and ideascapes; petitioners begin arriving from mortal worlds.
Mythic Age	Divine realms form within planes; gods claim domains and shape planar geography through belief, worship, and war.
Mythic Age	Baator (Nine Hells) and the Abyss consolidate into major evil powers; the Blood War begins (date indeterminate).
Early Ages	Celestia, Elysium, Arborea, and other upper planes formalize their celestial hierarchies and pathways.
Early Ages	Mechanus and the modron hierarchies establish planar routes and predictable cycles; lawful planar trade grows safer.
Early Ages	Ysgard, Limbo, and Pandemonium become "high-entropy" frontiers for exile, trial, and transformation.
Early Ages	The Outlands and the Spire become the neutral anchor for the Great Wheel; planar travel concentrates around the hub.
Ancient Era	Planar metropolises develop (including Sigil as the City of Doors); interplanar commerce becomes routine for elites.
Ancient Era	Alignment-based factions, sects, and philosophical cults spread across the planes; belief becomes a weapon system.
Middle Ages	The Outer Planes enter "cold war" patterns: proxy conflicts on primes, cult expansion, and negotiated divine borders.
Middle Ages	Planar cartography and portal-key lore proliferate; gate-towns rise on the Outlands as staging points to each plane.
Planescape Era	Faction influence peaks in Sigil and beyond; philosophical movements begin shaping policy, trade, and planar law.
Faction War	Factions implode into open conflict; the Lady of Pain intervenes, bans/dismantles factions, and forces a new status quo.
Post–Faction War	Power shifts from factions to guilds, cabals, mercantile blocs, and quiet divine proxies; portals remain the true currency.
Modern Era	The Blood War persists; planar travel continues under constant risk: portal politics, belief-engineering, and "friendly" heavens with strings attached.