Illusionist's Gambit

Instant

Cast this spell only during the declare blockers step on an opponent's turn.

Remove all attacking creatures from combat and untap them. After this phase, there is an additional combat phase. Each of those creatures attacks that combat if able. They can't attack you or planeswalkers you control that combat.

Creatures that didn't attack during the combat phase when Illusionist's Gambit resolved aren't required to attack in the additional combat phase, although they may. Those creatures can attack you or a planeswalker you control.
If, during a player's declare attackers step, a creature is tapped, is affected by a spell or ability that says it can't attack, or hasn't been under that player's control continuously since the turn began (and doesn't have haste), then it doesn't attack.
If there's a cost associated with having a creature attack, the player isn't forced to pay that cost, so it doesn't have to attack.