Walking Sponge

{T}: Target creature loses your choice of flying, first strike, or trample until end of turn.

Merfolk Thaumaturgist

{T}: Switch target creature's power and toughness until end of turn.

Riptide Mangler

{1}{U}: Change this creature's base power to target creature's power. (This effect lasts indefinitely.)

Mu Yanling

+2: Target creature can't be blocked this turn.
−3: Draw two cards.
−10: Tap all creatures your opponents control. You take an extra turn after this one.

Charix, the Raging Isle

Spells your opponents cast that target Charix cost {2} more to cast.
{3}: Charix gets +X/-X until end of turn, where X is the number of Islands you control.