Some undead Hellknights can command the bones of both their own bodies and others, and they primarily use this ability to temporarily strengthen themselves and summon waves of reinforcements. While just as undead as their compatriots, these so-called bonesingers have enough intelligence to join their living counterparts, though they're generally shunned and disavowed.
The bodies of Hellknights occasionally rise to continue their fight. This is just one example of an undead soldier of Hell.
HP 130, void healing; Immunities bleed, death effects, disease, paralyzed, poison, unconscious; Weaknesses holy 10, vitality 10; Resistances cold 10, electricity 10, fire 10, piercing 10, slashing 10
Reactive Strike
Trigger A creature within the monster's reach uses a manipulate action or a move action, makes a ranged attack, or leaves a square during a move action it's using.
Effect The monster attempts a melee Strike against the triggering creature. If the attack is a critical hit and the trigger was a manipulate action, the monster disrupts that action. This Strike doesn't count toward the monster's multiple attack penalty, and its multiple attack penalty doesn't apply to this Strike.
Void Healing
A creature with void healing draws health from void energy rather than vitality energy. It is damaged by vitality damage and is not healed by vitality healing effects. It does not take void damage, and it is healed by void effects that heal undead.
The skeletal Hellknight bonesinger strikes its rib cage three times, creating a loud, ominous clatter. All mindless skeletons in a 30-foot emanation must use their reaction to Stride closer to the bonesinger.
For the Cause(concentrate, manipulate, occult, void)
Frequency once per day
Requirements The skeletal Hellknight bonesinger has fewer than half their Hit Points remaining
Effect The bonesinger reaches out through the necromantic magic that animates the dead around them and pulls it into themself. The bonesinger chooses up to three mindless skeletons with the minion trait that they control within a 10-foot emanation and destroys them. The bonesinger regains 2d6 healing void Hit Points for each skeleton destroyed.
Invoke Reckoning(manipulate, occult, void)
Frequency once per round
Requirements The skeletal Hellknight bonesinger's last action was to damage an enemy with a melee Strike
Effect The bonesinger pulls at the bones of the creature they just damaged, releasing a pulse of void energy. That creature takes 4d8 void damage and must attempt a DC 23 Fortitude save.
Critical Success The creature takes no damage.
Success The creature takes half damage.
Failure The creature takes full damage.
Critical Failure The creature takes full damage and is Drained 1.