Valnir the Reaper

Wither, Mark of Nurgle. (This creature gets +0 /+1
and has intimidate.)
Whenever Valnir the Reaper deals combat
damage to a player or planeswalker, proliferate.
(Choose any number of permanents and/or players,
then give each another counter of each kind already
there.)
{b/g}{b/g}: Regenerate Valnir the Reaper.