Delirium is found across card and ability types, from instants to triggered abilities on permanents, but they all care about one thing: whether or not you have at least four card types in your graveyard
Let's go ahead and cover a short summary of each one
No troves, gift sets, or accessories seem to be being stocked
You cant cast those big game-breaking spells if you dont have the mana for them, and that's where these spells come in
This cares about Commander and multiplayer, but not formats like Type Four, Highlander, or Five Color or Pauper, just Commander specifically and multiplayer generally
Very hard to choose one as there is plenty of good work done every year, but I will go with the full art Grief by Campbell White