Siro the Deathbloom

Siro the Deathbloom enters the battlefield tapped.
When Siro the Deathbloom enters the battlefield, create a 1/1 green saproling creature token.
{t}, Sacrifice a creature you control: Add {b} to
your mana pool equal to the sacrificed creature's toughness.
All life must start from somewhere, and all life must
end somewhere. The Deathbloom is just very efficient."