This is the big guy: The boss monster to the crystaline claws and the other constructs in the arm. Intended to be about 500 to 1000 xp and encountered between levels 3 and 7.

Two questions right off: Is this about in the ballpark for it's budget, and should Usurping Bolt be able to make spell casters cast a spell? What about a Cantrip?

Crystal Commander
HP (68)
AC 16
STR DEX CON INT WIS CHA
22 15 18 5 10 18
Damage Immunities:poison, psychic
Condition Immunities:blinded, charmed, deafened, exhaustion, frightened, paralyzed, petrified, poisoned
Sword Strike: +7 2d6+6
Multiattack: The Crystal Commander makes two attacks with its sword.

This creature appears to be a suit of ornate and highly ranked, albeit dated armor. There is a large purple crystal underneath it’s helmet, glowing. Similar crystals are visible at all of the armor’s joints and on the backs of its gauntlets.

Antimagic Susceptibility: The Crystal Commander is incapacitated while in the area of an antimagic field. If targeted by dispel magic, the Crystal Commander must succeed on a Constitution saving throw against the caster’s spell save DC or fall unconscious for 1 minute.

Commanding Bolt: Up to two target Constructs within 30 ft either make their next attack with advantage or make a saving throw now to end an ongoing effect. Constructs that have failed their save against dispel magic awaken immediately.

Usurping Bolt: +4 Ranged Magical Attack. The Crystal Commander charges with infernal power, giving off arcs of bruise-purple energy. At the beginning of it's next turn, it targets one non-Construct within 30 ft. That creature takes 2d6 damage and must make a DC 16 Wisdom Save. On a failure, the target makes one attack against a target of the Commander’s choice.