Traits

Ossuary Sense. Knows the location of every skeleton, corpse, and pile of bones within 120 feet.

Bone Harvest. When a creature dies within 30 feet of the Bone Weaver, the Bone Weaver gains 10 temporary Hit Points.

Actions

Multiattack. Uses one Bone Spike and one Weave Barrier.

Bone Spike. Ranged Attack Roll: +5, range 60 ft. Hit: 10 (2d6 + 3) Piercing damage.

Weave Barrier. The Bone Weaver weaves a wall of bones at a point it can see within 60 feet. The wall is 10 feet long, 10 feet tall, and 1 foot thick, and provides Total Cover.

The wall has AC 12, HP 25, and has Vulnerability to Bludgeoning damage. When the wall is destroyed, its space becomes Difficult Terrain (bone fragments).

The Bone Weaver can maintain at most three walls at once. If it weaves a fourth, the oldest one collapses.

Grasping Bones (Recharge 5–6). The Bone Weaver raises bony hands from the ground in a 20-foot radius area. Every enemy in that area makes a DC 13 Dexterity save.

• Failure: The target is Restrained (escape DC 13, Strength check) and takes 9 (2d8) Piercing damage.
• Success: Half damage, not Restrained.

How to Use

The Bone Weaver changes the battlefield's architecture. With Weave Barrier, it:

• Separates the Fighter from the Wizard
• Cuts off the escape route
• Builds itself cover (Total Cover — can't be targeted directly!)
• Blocks ranged attacks

This is the sneakiest Controller. The other two spread conditions; this one builds geography.

Combination:

Bone Weaver (Controller) + 4× Skeleton (Brute)

The Bone Weaver weaves a wall, splitting the party in two. The Skeletons attack the weaker half. The other half is stuck breaking down the wall.

And Bone Harvest — every Skeleton that dies gives the Bone Weaver 10 temp HP. It feeds on the death of its own allies.

How the party wins: The walls are Vulnerable to Bludgeoning — a Warhammer/Maul brings one down in two hits. Or ignore the walls and focus on the Bone Weaver (if it's behind Total Cover, go around it).