Tortempest, Storm Charger

Whenever you cast your first instant or sorcery
spell each turn, exile an instant or sorcery card at
random from your graveyard. Then copy each
card exiled with Tortempest, Storm Charger.
You may cast these spells until your next turn.
Instant or sorcery spells cost {u}{b}{r} less to cast.
This effect reduces only the amount of colored
mana you pay.