I changed it to disadvantage; changes can be seen at the link at the top of the thread.Virtually always going last (which will happen unless the campaign's enemy selection is going to be very Illithid centric) would suck. At least disadvantage on initiative gives you a chance of beating a particularly slow enemy or two, or more in situations where you would otherwise have had advantage.
That was a trait taken from the Yuan-ti PC because it seemed to fit the Alhoon.The only trait the race gets that really seems terribly powerful is magic resistance (in the Alhoon subrace).
The Mind Blast mechanics where illithid flavor over a Dragonborn breath weapon mechanics.The race's Mind Blast is, apart from dealing half-damage on a save, largely equivalent to a single-target, limited-use cantrip with awful range. I'd drop the half-damage on a save and include some kind of rider to beef it up a little bit; maybe removing the ability to take reactions until the end of the Illithid's next turn. I'd probably also create a racial feat that makes the ability an AoE cone attack and that imposes disadvantage on attack rolls and ability checks on anyone who fails the save by 5+ until the end of the Illithid's next turn.
Tentacles were derived from Tabaxi claws except for the Ulitharid's long tentacles which are its main feature.The Tentacles trait is, honestly, just a melee weapon replacement. It has precious little mechanical value, but does some heavy-lifting flavor-wise.
I just tried to balance telepathy with other sub-race features so the magic resistant Alhoons don't get telepathy, the common do but with Mind Blast I nerfed it (I'm considering changing it back 30' though), and the Ulitharid got full 30' range.Also, why does the telepathy have such a short range? I'd have them all with a range no shorter than 30 feet. What I'd probably be most inclined to do is have it be dependent upon the character's Int score, say, 30 feet +5 feet per point of Int modifier.