yeah recharge 5-6... aaand thunder damage?
Oh yes, they changed the energy type's name from sonic to thunder in 5E.
Anyhow, Recharge 5-6 works for me, do you prefer a cone or circle for the AoE?
I'm thinking:
Earsplitting Trumpet (Recharge 5-6)[Cone]. The gurgohemoth uses its trunk as a magical trumpet. Each creature within a 90-foot[?] cone and able to hear the trumpet must make a DC 22 Constitution saving throw. On a failed save, a creature takes 13 (2d12) thunder damage and is deafened for 5 (1d10) rounds, and if the creature is size Large or smaller it is also stunned for 1 round. On a successful save, the creature takes half as much damage and isn't deafened or stunned. Gurgohemoths and gurgotches are immune to this attack.
Earsplitting Trumpet (Recharge 5-6)[Circle]. The gurgohemoth uses its trunk as a magical trumpet. Each creature within 60[?] feet of the gurgohemoth and able to hear the trumpet must make a DC 22 Constitution saving throw. On a failed save, a creature takes 13 (2d12) thunder damage and is deafened for 5 (1d10) rounds, and if the creature is size Large or smaller it is also stunned for 1 round. On a successful save, the creature takes half as much damage and isn't deafened or stunned. Gurgohemoths and gurgotches are immune to this attack.
Legendary Actions
Trumpet of Doom (Costs 3 Actions). The gurgohemoth broadcasts an Earsplitting Trumpet.
While I like the cone AoE just for the mental image of it "blowing its trunk and blasting creatures in front of it with the sound", I used the
Roar attacks of the
Androsphinx and
Dragonne) as models and they are both circle AoEs.
I also wonder whether we should increase the range. I set the cone to 90 feet to match an Ancient Red Dragon's breath weapon and eyeballed the circular version as having two-thirds the radius.
The Sphinx's roar is 500 feet radius and the Dragonne's is 120 feet.
The Dragonne Roar seems closer to our monster, as it can use it every 1d4 rounds rather than it being an ultrapotent X/day ability like the Androsphinx Roar.
So maybe we should use "Each creature within 200 feet of the gurgohemoth" for the AoE or possibly "Each creature within a 300-foot cone" or thereabouts?
We could tweak it a bit to, say, a 120/150/180 foot circle or a 180/200/240 foot cone?
I guess we could combine the two and let the gurgohemoth choose whether to affect a cone or a circle, like so:
Earsplitting Trumpet (Recharge 5-6)[Combined & Expanded]. The gurgohemoth uses its trunk as a magical trumpet. The trumpet affects each creature within 200[?] feet of the gurgohemoth or a 300-foot[?] cone, as the gurgohemoth chooses. Each creature in that area able to hear the trumpet must make a DC 22 Constitution saving throw. On a failed save, a creature takes 13 (2d12) thunder damage and is deafened for 5 (1d10) rounds, and if the creature is size Large or smaller it is also stunned for 1 round. On a successful save, the creature takes half as much damage and isn't deafened or stunned. Gurgohemoths and gurgotches are immune to this attack.
Which works for you the best?