Therion, Shackled Thief

Double Strike
{1}{u}{u}: Until end of run, when Therion,
Shackled Thief deals combat damage, add X {c} to your mana pool. Until end of turn, you
don't lose this mana as steps and phases end.
{1}{b}{b}: Target creature gets -2/-2 until end
of turn.
{2}{u}{b}: Gain control of target artifact.