Actions

Multiattack. The sun child uses its maddening presence and makes 5 attacks; 2 with its fists, 2 with its tentacles and 1 special attack. If a creature is hit by both fist attacks it takes an additional 13 2d12 bludgeonig damage.   Baby Fists. Melee Weapon Attack: +14 to hit, reach 5 ft., one target. Hit: 30 4d10+8 bludgeoning + 11 2d10 fire damage.   Solar Tentacle. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 28 8d4+8 radiant + 11 2d10 fire damage.  

Special Attacks

Rain of Fire (Recharge 5-6). The sun child conjures a rain of bronze flames in a 20-foot radius, 120-foot-high cylinder centered on a point within 40 feet.
Each creature within that cylinder must make a DC 21 dextarity saving throw.
On a failed save a creature takes 21 6d6 fire + 21 6d6 radiant damage.
On a successful save a creature takes half as much damage.   Solar Shrike. The sun child giggles, which diminishes every living creature within 60 ft of it.
Each creature in the area must make a DC 20 Constitution saving throw.
On a fail, they're reduced to half of their current hit points and are deafened for 12 seconds.
This attack has no effect on creatures that are deaf.
After using this attack the sun child can only take 1 legendary action until the beginning of its next turn.   Maddening Presence. Each creature of the sun child’s choice that is within 120 feet of the sun child and is aware of it must succeed on a DC 18 Wisdom saving throw or become frightened for 1 minute.
A creature repeats the saving throw at the end of each of its turns, ending the effect on itself on a success, and taking 10 4d4 psychic damage on a failure.
If a creature’s saving throw is successful or the effect ends for it, the creature is immune to the sun child's Maddening Presence for the next hour.

Legendary Actions

The sun child can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature’s turn. The sun child regains spent legendary actions at the start of its turn.   Move. The sun child moves up to its speed without provoking opportunity attacks.
Solar Tentacle. The sun child makes a tentacle attack.
Pounce (2 Actions). The sun child jumps up to 80 ft. and attacks with its fists against a target within its reach.