Gruhfex, Grim Manipulator

Whenever a land you control enters the
battlefield tapped, add {g}, {b}, or {r}. Until
end of turn, you don't lose this mana as steps
and phases end.
{1}{g}{b}: Target creature gets -X/-X until end
of turn where X is the amount of colors of
mana in your mana pool. If that creature dies
this turn, search your library for a basic land,
put it onto the battlefield tapped, then shuffle
your library.