The Dead Shall Serve

Each of the creatures you put onto the battlefield this way must attack its owner, not a planeswalker that player controls.

For each opponent, you may choose not to target any creature cards in that player’s graveyard.

If one of these creatures can’t attack its owner during any given turn (due to a spell or ability such as Chronomantic Escape, or because a player on the opposing team has gained control of it, for example), it may attack another player, attack a planeswalker an opponent controls, or not attack at all. If there’s a cost associated with having that creature attack its owner, you aren’t forced to pay that cost, so it may attack another player, attack a planeswalker an opponent controls, or not attack at all.

If there are multiple combat phases in a turn, each of these creatures must attack its owner in each of them that it’s able to.

If, during your declare attackers step, one of these creatures is tapped or is affected by a spell or ability that says it can’t attack, then it doesn’t attack. If there’s a cost associated with having that creature attack, you aren’t forced to pay that cost, so it doesn’t have to attack in that case either.