Behemoth, Swarmlord

Eminence — At the beginnning of your upkeep, if Behemoth, Swarmlord is in your command zone or
on the battlefield, you may pay {x} and create a copy of target Tyranid you control, where X the converted mana cost of the targeted Tyranid.

Double strike
Tyranids you control get +1/+1 and trample.
{1}, Sacrifice a Tyranid: Regenerate Behemoth, Swarmlord, then put a +1/+1 counter on it.