Bone Walker

Undead Fortitude. If damage reduces the Bone Walker to 0 hit points, it must make a Constitution saving throw with a DC of 5+the damage taken, unless the damage is radiant or from a critical hit. On a success, the Bone Walker drops to 1 hit point instead.

Presence of Death: Creatures with 100 ft of the Bone Walker have disadvantage on Death Saving Throws. 

Multiattack. The Bone walker makes two slam attacks. 

Slam. Melee Weapon Attack: +10 to hit, reach 15, one target Hit:  25(3d10+6) bludgeoning damage. 

Enervating Focus. Melee Weapon Attack: +10 to hit, reach 15 ft., one target. Hit: 24 (4d8 + 6) necrotic damage. The target must succeed on a DC 18 Constitution saving throw or its hit point maximum is reduced by an amount equal to the necrotic damage taken. This reduction lasts until the target finishes a long rest. 

Bone Cage. The Bone walker stabs it's hand into the ground and targets a creature it can see with 150 ft. The target must succeed on a DC 18 Strength or be restrained and take 5d8 bludgeoning damage.