A simple spell question

I was trying to make dark summoning work on targeting enemy units, and I set the targets to enemies only. When I tried it out, it said "Must target friendly units" or something like that, and when I tried it on my own units, it said "Must target enemy". Similar thing happened with mana drain (blood mage's spell) except I tired to make it target friendly only. :\
How would this be done?

If it does do thatr, then it means it's hardwired into the spell. You could trigger the abiltiy and make it manually, by basing a new abilty off of Channel and making a new trigger like:

Events
Unit - A unit begins casting an ability
Conditions
(Ability being cast) equal to Dark Summoning)
Actions
Unit - Move (Target of ability being cast) instantly to (Position of (Casting unit))

That's a pretty damn horrible trigger: *Never* use 'A unit begins casting an ability' for these things. Instead, use 'A unit finishes casting an ability' or 'A unit starts the effect of an ability'.

With 'begins', you can cancel the spell to avoid any mana cost or cooldown, but still get the effect.