Ethereal Form Morphing

I have a question concerning using the Orc Spirit Walker "Ethereal Form" ability: When the hero morphs using Ethereal Form (Renamed to "Phase" in this map) he is supposed to lose [10, 7, 4] mana per second until he becomes corporeal again; I accomplished this by making a spell based off of Immolation that does nothing but drain mana. The problem is that this trigger:
does not cause it to activate the immolation spell. The mana drain spell is inside a disabled spell book, which I suspected was the problem, but even having it enabled doesn't work. The morphing and demorphing spells work fine, but I can't get the mana drain to work. Is my wait not long enough, is there a better spell to use for the mana drain (I was contemplating using Siphon Mana), or is the trigger not detecting the unit in ethereal form correctly (I tried move and attack commands, and they worked fine)? Suggestions, please...

why not use the fountian of mana regeneration ablity?

-Av3n

Blast...I hadn't thought of that, but I had the nagging feeling there was some spell I wasn't remembering. Thanks!

I think there is a problem with negative values, though. If I uncheck the "percent" box and set the mana restored to "-1.00" it depletes 1 mana per second, thus taking 360 seconds to destroy 360 mana (This may only be because of the hero's mana regain counteracting the mana depletion, which is quite considerable). If I set the mana restored to "-3.00" it gets rid of mana at a much faster rate, and doesn't take anywhere near 120 seconds to deplete a mana pool of 360 mana. Is there a way to check the interval on this, or have I done something wrong? Check it for yourself, and I can get more exact numbers if you want.

Hero regen is constant. Same reason why +10% revenue and increase profits 200%.

Ok, so would it be better to use immolation fore the mana drain then?

Yes, otherwise the hero mana regen will almost counter the drain.