Tainted Growth

At the beginning of your upkeep, creatures with 'Concerning Symptoms' get -1/-1 and lose all
abilities.
Where a creature dies due to Tainted
Growth, create 2 Leftovers creature tokens on
owner's battlefield. (Owner of Tainted Growth
decides the placement of these tokens.)

At the end of your turn, if 6 or more Leftovers
creature tokens are on the battlefield, replace
Tainted Growth with Dangerous Mutations.