Write me a D&D 5e campaign module for a party of 3-5 adventurers. The setting should take place in the world of Planescape, beginning in the city of Sigil and traversing all of the inner and outer planes, astral plane, and ethereal plane. The party should begin at 1st level and reach 20th level by the conclusion of the adventure. The module should consist of 4 distinct chapters, each representing a "tier" of D&D 5e play as per Adventurer's League rules. Provide challenge-appropriate encounters for the party with predetermined loot and treasure rewards. There should be at least two named evil NPC villains, one of which is the "mid-boss" of the second chapter, and the other who is the ultimate enemy of the campaign; however you should create more as appropriate.
go outside