Also, I believe the mana gets used up as soon as the spell is cast (before releasing it, if it's a targeted spell). Even if you could cancel the spell, the mana would already have been spent.

Ah okay, thanks both of you. I figured it might of not spent the mana on spells that need to be activated twice, one for incantation and one for casting but guess I was wrong. That stinks though, guess I'll just have to deal with it lol.

Keep one of the wands of Magic Arrow handy. One poke with it will almost always bring the lurker right back to you, even if it is running away. Also, you can try taking a blind shot, shooting after it in the dark. The missile might still hit if you're not too slow.

That's good to know, thanks. I was unsure if the shot would keep going till it impacts a wall or something after a certain point or dissipate after a set distance but that answers that question :D.

It might dissipate eventually, but I don't know what the distance for that is. I do know that any dissipation distance is beyond lantern light range.

Dissipation generally doesn't come up, because by the time it might be an issue, the monster has probably moved out of the flight path anyway.