Relentless Assault (CMR)

Sorcery

Untap all creatures that attacked this turn. After this main phase, there is an additional combat phase followed by an additional main phase.

Christopher Moeller
416/361
uuid: b98497be-5df9-5882-a86f-eed03c62e206

2004-10-04:
If you manage to cast this during a main phase of your opponent’s turn, that opponent’s creatures will untap and that opponent will be able to attack again. It will not allow you to attack during their turn.
2004-10-04:
Abilities that trigger when a creature attacks, blocks, or is blocked will trigger during each combat that turn. Thus, a creature with Rampage will get the bonus added during each attack.
2004-10-04:
A creature that must attack each turn, must only attack once that turn. It is not forced into each attack that turn.
2004-10-04:
It only creates an additional combat and main phase if it resolves during a main phase.