Inverse Immolation

Inverse Immolation

I made a spell called soulfire, its basicly an inverse imolation where me demon hunter's arss get's burned but he burns away mana from the enemy, the problem is I can make my demon hunter's life drain but I cannot make the other units mana to wash out.
I tried making an ability like a brilliance aura with negaive factors that would have a reduced range called soulfire effect (I made 4 one for each level of soulfire) ,but ther is no way I can add my demon hunter that ability when he casts soulfire, Ill show u my trigger.

Event
Unit - A unit Begins casting an ability

Conditions
(Ability being cast) Equal to Soul Fire
(Level of Soul Fire for (Casting unit)) Equal to 1


Actions
Set PyroCaster = (Casting unit)
Unit - Add Soul Fire (Effect) 1 to PyroCaster

And another trigger that goes:

Event:
Unit - A unit Finishes casting an ability

Condition:
(Ability being cast) Equal to Soul Fire
(Level of Soul Fire for (Casting unit)) Equal to 1

Action:
Unit - Remove Soul Fire (Effect) 1 from PyroCaster

How else could I do it?

im not sure theres an event that registers a unit toggling a toggleable ability.

Is it starts the effect of an ability or something?

Nah.

Begins casting ability - Comes in range, has enuff mana ( by this point the order can be stopped, and this acts be4 cast time )

Starts effect of ability - After Cast Time is done. By this point, the spell will have to cool down if it is stopped ( channeling spells )

Finishes Casting Ability - The Effect of an ability naturally finishes ( channeling spell runs out of time, full flame strike has appeared, etc )

Stops Casting Ability - The effect of an ability Artificially OR Naturally finishes ( same as Finishes Casting Ability, + counts things like prematurely ending a channeling spell )