Varasig, the conglomerate

Varasig gets +1/+1 for each other eldrazi you
control.
Whenever Varasig attacks, exile the top card of
defending players library.
You may cast spell exiled by eldrazi sources and
spend mana as if it were mana of any colour.
Creature spells you cast from exile have devoid
and are eldrazi in addition to their other types.