Ta’olus, The Storm Lord

When Ta'olus, The Storm Lord is put into the graveyard or exile from anywhere, you may put it
into your library fourth from the top.
Flying, trample, double strike.
Whenever you cast a noncreature spell, add one
mana that is {u}, {r} or {g}.
You don't lose unspent mana as steps and phases
change until the end of each turn.