Otto's Thermos

Ward-Discard a card.
Defender
When Otto's Thermos enters the battlefield,
create X tapped Treasure tokens.
{u/b}, {t}, Sacrifice an artifact: Otto's Thermos
phases out.
Long as Otto's Thermos was crewed this turn,
you gain hexproof until end of turn.
Otto's Thermos' toughness is equal to the
number of artifacts you control.
Crew 1