one tiny tidbit you might want to learn, is if you want the fire to do increasingly higher damage, you have 3 options (one which doesn't work)
a) you make a levelable immolation spell (doesn't work)
b) you make 4 skills corresponding to each level and use way more triggers than are needed. (not suggested cause #3 is best)
c) you give them an actiavatble immolation ability and give that 1 ability X amount of levels. Then when the unit is spawned, set the level accordingly of the act. immo. and order them to activate the ability.
For some reason, a) makes the immolation only work on level 1, so i've found out that c) is the best way to do this, that is, if you're making the fire do more damage depending on the level.
This might help, or it might not, but either way, it's good to know for making spells like this with as little triggers as possible.
BTW when i'm talking about immolation that doesn't work, i mean passive perm. immolation (like what infernals have.) Naturally it does work, but you can't set it to work properly with triggers.