Agyrem

If a creature is put into a graveyard from the battlefield, its last existence on the battlefield is checked to determine its color.

If multiple creatures are put into their owners' graveyards at the same time (due to combat damage or Planar Cleansing, for example), Agyrem's first two abilities trigger that many times. At the beginning of the next end step, the player whose turn it is at that time puts all of their Agyrem delayed triggered abilities on the stack in any order, then each other player in turn order does the same. The last ability put on the stack is the first one that resolves. The creatures are returned one at a time.

If an ability of a plane refers to "you," it's referring to whoever the plane's controller is at the time, not to the player that started the game with that plane card in their deck. Many abilities of plane cards affect all players, while many others affect only the planar controller, so read each ability carefully.

Agyrem's first and second abilities each set up a delayed triggered ability. These abilities will trigger at the beginning of the next end step even if Agyrem is no longer the face-up plane card.

If you're affected by the chaos ability, creatures will still be able to attack planeswalkers you control.

Agyrem's first ability will return a card to the battlefield only if it's still in the graveyard by the time the delayed triggered ability resolves. Similarly, Agyrem's second ability will return a card to its owner's hand only if it's still in the graveyard by the time the delayed triggered ability resolves.