I just need a unit to be able to cast an effect on a friendly unit. Having it splash and hit nearby units would be a plus.
...
Come to think of it, would a modified version of the attack skill be useful for this? AFAIK, all it really needs is to not do damage (aside from the effects), and for the AI to hopefully know to use it on the targets that it affects. Then we could even have pretty projectiles and such from the attack skill.
Done, with some loose ends to tie up no doubt
It is not based on attack 'as such', projectiles and splashes were only very loosely tied to attack skills anyway, but it works in much the same way.
I gave merlin a modified version of your 'healing light' spell, check that for the 'full scoop'. In a nutshell, make the command <affect value="target"/>, add a <start-time value="0.x"/> to the skill, and optionally a Projectile and/or splash.
*start-time is technically optional, but the default is 0.0, which is probably not what you want...
**internally this is
very similar to how attack works, and indeed uses a lot of the same code, as such the whole skill-speed Vs anim-speed problems that exist with attack exist with cast-spell too, in particular the start-time is tied to the anim-speed, not the skill speed. Use the same value!