Will is thrown a bit by the cackle, but shakes it off with no ill effects.
Taking this as a sign that Callah is too tired to present a threat for the rest of the round, the lore-master sets his sights on the most energetic-looking of the imps.

William throws a Fireblast at Abacus!
Damage: (4d7+3)[14]
15 MPP - 7 MPP -> 8 Magic Power Points remaining