This is going to be an early boss for my upcoming campaign. I have 7 5th-level player characters, and this fight is meant to challenge them quite a bit. There will also be a few minions.
The story is that this quaggoth found a dying dryad and consumed her heart, this made him a sorcerer as well as giving him some druid magic. Then the cult of the dragon found him and made him a half dragon. If the players don't kill him I plan on making him an NPC later on.
I would like to know if this monster is ready to be thrown at my players, if it is too overpowered or underpowered at its current challenge rating, and what I can do to fix any balancing problems found in the stats of this monster.
Half-dragon Quaggoth Thonot (4th-level sorcerer)
Armor Class: 16 (permanent Barkskin)
Hit points: 48
Str (16; +3) Dex (12; +1) Con (16; +3) Int (8; -1) Wis (12; +1) Cha (14; +2)
Saving Throws: Str +6, Con +6
Senses: Treill has blindsight out to 10 ft, and darkvision out to 180 ft.
Wounded Fury. While he has 10 hit points or fewer, Treill has advantage on attack rolls. In addition, he deals an extra 7 (2d6) damage to any target he hits with a melee attack.
Multiattack. The quaggoth makes two claw attacks.
Claw Attack. Melee Weapon Attack: + 5 to hit, reach 5 ft., 1 target. Hit: 5 (1d6 + 3) slashing damage.
Lightning breath Recharge (5-6). Treill can use his action to exhale destructive energy. Each creature in a in a 5 by 30 ft. line must make a Dexterity saving throw or take 24 (7d6) lightning damage, or half as much on a successful save.
Spellcasting. Treill is a 4th-level caster; his casting ability is Charisma. Spell save DC 13; +5 to hit with spell attacks.
Cantrips (at will) fire bolt, sword burst, poison spray, predestination, toll the dead.
1st level (3 slots): color spray, magic missile, shield.
2nd level (2 slots): invisibility, spider climb.
Innate spellcasting. Thonot DC 12. +4 to hit.
At will: mage hand, feather fall.
1/day: Cure wounds, enlarge/reduce, heat metal, mirror image.
Magic initiate (druid). DC 12, +4 to hit with spell attacks.
Cantrips: Thorn whip, druidcraft
1/day: healing word