Precedents

Lightning
Lightning will blow through wooden doors and sets things that are flammable and not living on fire. Wood with metal banding has a chance of reflecting back. It will bounce. In a “Uturn” or “Sbend” you must be straight to the first corner to bank it, and you have 50/50 of banking the second corner.

Illithid Fwooping
Does not go through walls.

In general:
Spells can’t go through walls. (Teleport does not go through a wall … You cease to exist and reappear somewhere else.)

More lightning. More shooting. They win eventually.

Precedents

Big trouble in Baldur's Gate Twinkletwit