Noticed a typo in my previous post. It was meant to be
Hit Points 127 (15d8 + 60) but it got a stray 5 instead of a 6 there.
Subtypes should be "Gnoll, Shapechanger" not just "Shapechanger" and I'd cut the "Typically" from the alignment.
For the ability scores, is INT 9 (-1) a bit high? A standard 5E Gnoll is INT 6 (-2). Gnolls got dumber from 1E AD&D where they had Low-average Intelligence to Low Intelligence in 2E and the Ghuuna is a 1E monster. I'd prefer INT 7 or 8 myself.
Ghuuna are vulnerable to cold iron weapons and magic weapons, not silver ones. Nonmagical silver weapons are useless against them.
The passive perception should be 11 not 12 if it has WIS 13 (+1) and no Perception proficiency.
That said, I suggest Perception +3 and passive Perception 13 like a
Giant Hyena.
I wondered about whether its
Shapechanger should mention the hyena form is Large, based on the precedent of the
Werebear having "polymorph into a Large bear-humanoid hybrid or into a Large bear" in that Special Trait's description.
Hmm… does that mean a
Weretiger stays Medium sized in tiger form despite standard tigers being Large in size? I'd rather clarify the size, like so:
Shapechanger #2. The ghuuna can use its action to polymorph into a Large giant hyena, or back into its true form, which is humanoid. Its statistics, other than its size and AC, are the same in each form. Any equipment it is wearing or carrying isn’t transformed. It reverts to its true form if it dies.
Alternatively, how about adding a hybrid form:
Shapechanger #3. The ghuuna can use its action to polymorph into a Large hyena-humanoid hybrid or into a giant hyena, or back into its true form, which is humanoid. Its statistics, other than its size and AC, are the same in each form. Any equipment it is wearing or carrying isn’t transformed. It reverts to its true form if it dies.
The original description doesn't mention a Hyena-gnoll form, but there are shapechangers that don't have hybrid forms in AD&D but can assume a beast+humanoid shape in later editions.
It doesn't need
Hyena Empathy. The
Monster Manual says werewolves form packs that include wolves and dire wolves but 5E doesn't bother granting that lycanthrope
Wolf Empathy.
I gave it feint and parry (instead of a shield but giving it a bit of a shield flavour) - idea of an energised and skilful flow.
Those Bonus Actions and Reactions all seem superfluous to me.
I like the
Rampage trait from the SRD giant hyena but don't see why it needs anything added. The standard lycanthropes don't have two or three action options bolted on to them but are mechanically relatively simple.
According to the original article these creatures tend to be encountered in small packs of two to five ghunna plus an equal number of giant hyenas or twice their number of regular hyenas, so we don't want them to be individually complex as there'll be a bunch of hairy brutes on the battlefield to keep track off. That's not even considering that there'll likely be regular gnolls around the place as well.