I'll go along with "Wraith" as well, after all, it's a boss type enemy. And yes, the Greatest Ghost does sound a bit corny.
I've looked up the stats for the Greater Ghost, and amended the slightly to get the following:
"Wraith"
Health: 90
Speed: 3
Attacks: Mind Blast (Range: 1, Damage: 16), Cryo Blast (Range: 2, Damage: 19), Cryo Cross (Range: 1-2 Omnidirectional (Diamond shape), Damage: 13), Inhabit (Range: 1; Damage: none*)
Immunity: Physical
Resistance: Cold
*Inhabit can only work if the target's hp is equal to, or less than 5, works by the Wraith taking the host body, extracting the host soul, then restoring the new body to full hp.
Keeps the same attacks as before, since the attacks known are not bound to the body, but to the experience of the spirit/soul which inhabits it. Given that the Wraith used to be human, all the Psy attacks do not rely in some way or other on the owners body, so can be used with a body of any species (e.g. Spriggats are limited to their bodies for their elemental attacks, the Shadowport is also limited to Shadowlings body, etc).
Any thoughts on this?
Also, which other enemy set do you feel is not complete and needs additions?
What do you think of the Helenite unit set? Any suggestions? (There are a few golem ideas that were proposed for the Helenites, including using Dorgon-type golems, rather than Energy Golems, 'cause Helena had access to Dorgon.)