Multiattack

The fellforged makes two necrotic slam attacks.

Necrotic Slam

Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 11 (2d8 + 2) bludgeoning damage plus 4 (1d8) necrotic damage, and the target must succeed on a DC 14 Constitution saving throw or its hit point maximum is reduced by an amount equal to the total damage taken. This reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0.

Violent Escapement

With little regard for the clockwork bodies they inhabit, fellforged wraiths can stress and strain their mechanisms in such a violent manner that flywheels become unbalanced, gears shatter, and springs snap. As a bonus action, this violent burst of gears and pulleys deals 7 (2d6) piercing damage to all foes within 5 feet who fail a DC 14 Dexterity saving throw. Each use of this ability imposes a cumulative reduction in movement of 5 feet upon the fellforged. If its speed is reduced to 0 feet, the fellforged becomes paralyzed.