What's it with yugoloth images and weirdly glowing eyes, anyway? At least it's justified on this one.
Ultroloths have a chassis that's basically Exactly What You'd Expect. DR/Good, energy resistances, SR, Overwhelmingly Average Ability Boosts With A Focus On Constitution, Telepathy...
The ultroloth's combat ability is supposedly based on a trio of special abilities: Summon Yugoloth, its SLAs and Hypnotic Gaze.
The former is as unreliable as always (35% chance), but hey, I suppose 1-4 nycaloths are decent muscle for that one encounter every three days.
The latter is overwhelmingly average: it doesn't really function in combat situations, can hit allies, is mind-affecting and doesn't do all that much even if it connects.
The SLAs, while at first glance impressive, are honestly not that impressive. Sure, the ultroloth has a lot of options, but they're all very underwhelming for an 18 HD creature. Invisibility, Deeper Darkness, Desecrate, Suggestion, Scorching Ray... that's magic I expect on a low-level caster NPC, not a leader of daemonic armies. Even it's higher-level magic (Binding, Enervation, Symbol of Death) is inferior to what a caster could be using by now. If you're playing an ultroloth, expect to be reduced to shooting Scorching Rays after only one or two encounters.
Is the ultroloth comparable to a wizard, a sorcerer, or even a bard of equal level? Definitely not, and that answer alone should tell you that this is going to be -0 LA. I'm not saying the ultraloth can't make it as a PC: it has good defensive abilities and the tools to function in several scenarios. It is, however, going to be weaker than any comparable class (unless we stretch the definition of 'comparable' to an unreasonable extent).
-0 LA: when at ECL 18 your to-go spell in combat is 2nd-level, something somewhere has gone terribly wrong.