Celestreon Battlemage

When Celestreon Battlemage enters the battlefield, if it was casted, search your library
for an instant or sorcery spell that has a mana
cost equal to the amount of instant or sorcery
spells that entered your graveyard this turn.
Channel— {u}{w} : Discard this spell and an
instant or sorcery spell. Search your library for a Island or a Plains and put in on the battlefield.