hi
i played DotX. one of the Tank's spells is to summon 4-5 dark templars.
so my question is how i can detect the location of a unit.
i need that to set the mana of enemies' units to 0% to save my units from mind control, psi storm, etc.

You can just disable the abilities using Tech Settings.

Use the Move Location trigger.... It'd move the location on a unit. So you can move it onto your tank.

I made the more popular versions of DotX (v1.3 - v1.71), so I can help you with insider info:
The heroes have locations following them for XP giving. Don't know the names off the top of my head, but check XP triggers and you'll see.
These locations are rather large; about the range of a reaver shot. If that's enough just use this location and set all energy of P4 or P8 to 0.