This was my first upscaling of a monster in 5e. I just took a standard gargoyle, looked at the DMG how to upscale its power and, as if by magic, Gruethur appeared. I like the thematic nature of this guy but he didn’t last very long in battle.
Armour Class 15 (natural armour)
Hit Points 58 (7d8+21)
Speed 30’ ft., fly 60 ft.
Str 15 (+2) Dex 11 (+1) Con 16 (+3)
Int 6 (+2) Wis 11 (+0) Cha 7 (-2)
Damage Resistances bludgeoning, piercing, and slashing from nonmagical weapons that aren’t adamantine.
Damage Immunities poison
Condition Immunities exhaustion, petrified, poisoned
Senses Darkvision 60 ft., passive Perception 10
Languages Terran, Gothic but cannot speak
Challenge 4 (1,100 XP)
False Appearance. While the gargoyle remains motion less, it is indistinguishable from an inanimate statue.
Multiattack. The gargoyle makes two attacks: one with its bite and one with its claws.
Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target.
Hit: 6 (1d8 + 2) piercing damage.
Claws. Melee Weapon Attack: +5 to hit, reach 5 ft., one target.
Hit: 5 (1d6 + 2) slashing damage.
Gore. If the garogoyle hits with both its claw and bite it attack it may make a gore attack as a bonus action.
Melee Weapon Attack: +5 to hit, reach 5 ft., one target.
Hit: 8 (2d6 + 2) slashing damage.
Meyanda’s deadliest minion —a lumbering slate-gray gargoyle named Gruethur. The gargoyle has adorned himself with bits and pieces of dismantled machinery, scrap metal, and strips of wiring, but this is more an affectation and a misguided attempt to make himself into something more like Hellion than anything truly protective. The gargoyle is a mute, its throat a mass of scar tissue from the battle it lost months ago to Meyanda, after which it became her devoted acolyte when she decided to spare his life. Gruethur fights eagerly and to the death, but does not pursue foes beyond this room—his goal is to prevent entry into the reactor core.