Shai-Hulud, Dune Avatar

Eminence— As long as Shai-Hulud, Dune Avatar
is in the command zone or on the battlefield, attacking Wurms you control gain wither.
(Creatures with wither deal damage to other
creatures in the form of -1/-1 counters)
Trample, haste, reach
{t}: Tap three deserts, until the end of turn,
creatures you control gain unblockable.