Zera Feit, the Well of Power

{t}, Pay 3 life: Add one mana of any colour.
{3}{w}{u}{b}{r}{g}, {t}: You may cast a spell from
your hand without paying its mana cost. If you
do, it gains cascade until end of turn.
{12}: Until end of turn, Zera Feit, the Well of
Power becomes a 10/10 Elemental creature with
trample. Activate this ability only if your life total
is at least 10 lower than your starting total.