Stubborn in the Face of Danger. The Builder Des Calcites has Advantage when making a saving throw to resist becoming frightened
Chalky Skin. Builder Des Calcites' rocky ochre skin grants Advantage when making a Stealth (Dexterity) check to hide in rocky terrain.
Spellcasting. Des Calcites is a 9th level spellcaster. His spellcasting ability is Charisma (+7 to hit with spell attacks, spell save DC 15). He regains its expended spell slots when it finishes a short or long rest. He knows the following warlock spells:
Cantrips (at will): chill touch, mage hand, minor illusion, spare the dying
1st–5th level (3 5th-level slots): aura of life, banishment, blindness/deafness, contagion, death ward, enhance ability, false life, feign death, legend lore, ray of sickness, silence, speak with dead, stone shape, suggestion
Dark One’s Own Luck (Recharges after a Short or Long Rest). When the warlock makes an ability check or saving throw, it can add a d10 to the roll. It can do this after the roll is made but before any of the roll’s effects occur.
Dwarfen Hammer. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 3 (1d6) bludgeoning damage plus 10 (3d6) fire damage.