Target player gains control of up to three target nonattacking creatures until end of turn. Untap those creatures. They block this turn if able.
11/7/2014 The controller of the creatures still chooses which attacking creature each of the three target creatures blocks.
11/7/2014 Each of those creatures blocks only if it’s able to do so as the declare blockers step begins. If, at that time, one of the creatures is tapped, is affected by a spell or ability that says it can’t block, or no creatures are attacking that creature’s controller or a planeswalker controlled by that player, then it doesn’t block. If there’s a cost associated with having the creature block, the player isn’t forced to pay that cost, so it doesn’t block in that case either.
11/7/2014 Notably, Domineering Will doesn’t give any of the target creatures haste. Unless they have haste due to some other means, they won’t be able to attack that turn.