Atrax, Jeskai Striker

Whenever you cast an instant or sorcery that
targets Atrax, Jeskai Striker, you may counter that
spell. If you do, Atrax, Jeskai Striker gains +X/+0,
and haste until end of turn where X
is equal to the mana value of the spell. Exile that
spell.
{3}: Put target instant or sorcery exiled by Atrax,
Jeskai Striker into your hand. Exile that spell
at the end of the turn.
"What's gone is not forgotten"