Crag Troll

Regeneration. The troll regains 10 hit points at the start of its turn. If the troll takes acid or fire damage, it regains only 5 hit points at the start of its next turn. The troll dies only if it is hit by an attack that deals 10 or more acid or fire damage while the troll has 0 hit points.

Narrow Profile. The Crag Troll is so narrow from either side, that any attacks made against it are likely to miss. All melee attacks made from either side of the Crag Troll are made at disadvantage, even if they would normally be made at disadvantage. Ranged weapon or spell attacks automatically miss. Ranged weapon and spell attacks from directly in front of or behind the Crag Troll automatically hit (but should still be rolled to see if there is a critical hit). Additionally, the Crag Troll takes up a space that is 1' by 15'. 

Multiattack. The troll makes one Bite attack and four Claw attacks.

Bite. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 10 (1d8 + 6) piercing damage plus 5 (1d10) poison damage.

Claw. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 16 (3d6 + 6) slashing damage.

Flatten (Recharge 5–6). Each creature within a 15' by 15' area directly in front of or behind the Crag Troll (one or the other) must make a DC 19 Dexterity saving throw, taking 44 (8d10) bludgeoning damage on a failed save, or half as much damage on a successful one.

Dimensional shift. The Crag Troll may spend half of its movement (from the upcoming turn) to turn it's body up to 90 degrees in either direction.