Also what exactly is The Deck Of Dragons ??
It's the universes version of the Tarot deck. It is tied directly to the gods and the warrens, changing as the fortune changes. They come in houses: Light, Dark, Shadow, Life, and Death I believe. Think of them as suites. There are also some unaligned cards. Then each house has positions: King, Queen, Knight, Magi, Herald, Soldier, Spinner, Mason, Virgin. These titles can have different names for different houses. Like Mason is only in Death. He's called Builder in other suits.
Each of these cards represents a god or an Acendant or a person. They are always changing who holds the lesser roles, while the Major roles (King, Queen) don't change much because they are usually held by the most powerful god aligned to that aspect. These cards can then be used to tell the future and show how the various gods/ascendants are involved with the world and events.
It can help to think of the Malazan world in D&D terms (because this shared universe of Erickson and ICE came out of their shared D&D campaigns they ran together, building their world and also why the two authors disagree on somethings, like what sex K'rul is. It is also why they write in different parts of the world. In fact, the whole backstory about the Emperor, Dancer, Laseen, etc. is based on their actually D&D campaign). So if you've played D&D Ascendants is like hitting Epic Level on your character sheet. You've gotten so powerful you've moved past regular mortals. You're ot a god, but you're hanging with them and you might become one if people worship you enough. Warrens, then, are like the various Planes of the D&D Universe, Plane of Shadows, the Elemental Planes, the Astral Plane, etc.