Grimoire of Forbidden Studies

when Grimoire of Forbidden Studies enters add
3 decay counters (in the beginning of your upkeep
on the third turn this spell was casted, sacrifice this
card when it reaches 0.)
spells casted by opponents cost {5} more unless
they sacrifice 4 creatures they control unless they
exile 4 cards from hand into.

"sometimes its necessary to study the unbearable."