Egregoria, Haven of Regents

Dragons spells you cast cost 2 less to cast and
have, "As an additional cost to cast this spell,
discard of card."
Dragon Lands you tap give an additional mana for
each Dragon on the battlefield.
{w}{u}{b}{r}{g}, {t}: Add {g/u}, {r/w}, {u/b}{u/r}, {b/r}, or {w/u} to
your mana pool.