Ghroth, the Harbinger

Whenever Ghroth, the Harbinger enters the battlefield from anywhere other than exile, exile
it.
Whenever Ghroth enters the battlefield or
attacks, you may search your library for an
Eldritch creature, put it onto the battlefield
tapped, then shuffle.
{2}{u}{b}{r}{g}: Return Ghroth from exile to the battlefield tapped. Activate this ability only if
there are four or more Eldritch creatures you own
in exile.