Mists of deception make my 8 Marble Oracle dead?

[Twan]

Actually in defense no need to use another BE, Mist of Deception + retreating caster just allow the defender to win everytime (and kill any attacker still on the battlefield when turn limit is reached).

But if the caster remains 5 rounds or more on the battlefield, giving reasonable chances to kill him, usual MP rules (most hosts) consider this spell valid.