Lock-on Enemy

Cantrip (This spell consumes no mana, but can
only be cast if you have at least 1 mana available
of the corresponding color. Only 1 spell with
Cantrip can be active at a time).
Choose an enemy at the beginning of Combat.
You get +2 on your attack rolls against it, and -2
on your attack rolls on anyone else.
His eyes never strayed from his enemy, the same
as an animal with it's prey.