Judicator sometimes manipulate other beings' minds. Complete and total mind control would be possible, I think. The Dark Templar injects a portion of its essence into the target being, and restructures the mind of the being. The mind is nothing but the result of biological processes. Why can't we re-wire it?
We are talking about assassination, correct? Well, if a target is worthy of assassination, they'd probably know about it, and will protect themselves; they won't just be out in the open in some clear field. If they are some government or military official, they'll lock themselves behind some large doors in an installation somewhere. If we get passed the part where the assassin breaks through security, a long-range sniper rifle shouldn't be too helpful. In fact, more likely than not, to get through and battle at near-melee ranges. (Hence the psi-scythe.) Now remember, a Dark Templar has shields, do deflecting a few shots should be no concern.
Now, consider Nova's abilities: super-speed, psi-sight, strength, et cetera. Now, she is a lowly human; humans have only been exploring their psionic abilities for a few decades. Now look at the Protoss, whose innate psionic energies flourish. Would they not only possess similar abilities, but better ones?
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