Shai-Hulud, the Maker

The Passing of the Wurm - Whenever a Sand or
Wurm creature enters the battlefield under your control, if this card is in the command zone or on
the battlefield, hoard 1.
Wurm and Sand creatures you control have haste
and vigilance.
This spell costs {x} less to cast, where X is the
amount of times you've scried this turn plus the
number of deserts you control.