Ratatotskr, the Defiler

At the beginning of your upkeep, create
an Acorn token, that has, "{t}: sacrifice this
token; search your library for a basic forest
and put it into play, then shuffle your library."
Whenever a Forest enters the battlefield, put
a +1/+1 counter on each creature you control.
If Ratatotskr, the Defiler would die, exile it
instead, then return it to the battlefield at the
beginning of your next upkeep.