Slugmire, Spawn of Slimefoot

Slugmire, Spawn of Slimefoot enters the battlefield with a number of +1/+1 counters on
it equal to the number of creatures in target graveyard.
Whenever another creature dies, put a +1/+1
counter on Slugmire.
{x}, Remove X counters from Slugmire: Create X
1/1 green Saproling creature tokens.
{1}{b}, Sacrifice a Saproling: Regenerate Slugmire.