Ok so spells I had these...but some like magic missle could be swapped out pretty easily.
Cantrips (at will):
friends,
light,
poison spray,
prestidigitation, vicious mockery
1st level (4 slots):
command,
inflict wounds,
magic missile,
shield of faith
2nd level (3 slots):
dust devil,
hold person
3rd level (3 slots):
counterspell,
stinking cloud,
wind wall
4th level (3 slots):
dominate beast (flying only),
giant insect (flying only)
5th level (1 slot):
infernal calling (but summons a vrock)
The spells up to 3rd-level look fine to me, but the higher level ones are problematic.
Firstly,
dominate beast (flying only) overlaps with its
Enslave Aerial Creature" ability, which does the same thing except it affects any type of flying creature rather than just flying beasts.
That seems redundant.
Secondly, I don't believe
infernal calling is an SRD spell and, even if it was, I would be against having the Exalted Thrall summon a Vrock unless you want to seriously boost the Challenge Rating.
If the thrall's
Challenge incorporates a CR 6 Vrock and three to nine CR 1 Demon Locust Swarms it's going to end up at a CR higher than the +3 Proficiency Bonus band we're currently aiming at.
Thirdly, I'm fine with
giant insect, since it summons roughly CR 3 worth of creatures. That's basically the same as the three CR 1 demonic locust swarms its
Breath of Pazreal conjures so should be more-or-less balanced.
That said, I would rather use "(wasp only)" instead of (flying only) since they're the only flying insect option for the SRD
giant insect.
Come to think of it, we statted up a giant horsefly for 5E. How about adding that as an alternative giant insect?
Something like "
giant insect (wasps or flies*)" with the asterisk linking to a note saying "The exalted thrall's
giant insect spell can transform up to five wasps or three flies. A fly becomes a giant horsefly (see Giant Tabanid for statistics)."
Now I'm tempted to add "ten giant locusts" as an option, but we'd have to stat those up.
As far as I know there isn't an official 5E Giant Locust, although they do exist in earlier editions of D&D.