Gelatinous cube

Defender, Wither
You may choose not to untap Gelatinous Cube
during your untap step.
{t} Tap target attacking creature. It doesn't untap during its controller's untap step for as long as Gelatinous cube remains tapped. During your
upkeep place a -1/-1 counter on this creature and
a +1/+1 counter on Gelatinous Cube.