Jace, Wizened Chronomancer

Flash, Hexproof
When Jace, Wizened Chronomancer enters the battlefield, you may have an additional main phase after this phase. If it's not your turn, you may untap up to three target permanents.
{1}{b}, {t}: Destroy target creature. Activate this ability only on an opponent's turn, and only at any time you could cast a sorcery.