Cave Troll

Keen Smell. The troll has advantage on Wisdom (Perception) checks that rely on smell.

Regeneration. The troll regains 10 hit points at the start of its turn. If the troll takes acid or fire damage, this trait doesn't function at the start of the troll's next turn. The troll dies only if it starts its turn with 0 hit points and doesn't regenerate.

Battle Cry.  The cave troll, usually the leader of a small band of other trolls, will start an encounter by roaring to the sky above.  All other trolls within hearing of this will make their next attacks at advantage. 

Multiattack. The troll makes three attacks: one with its bite and two with its pick axe. 

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 7 (1d6 + 4) piercing damage.  Anyone bit by this attack must make a Constitution Saving Throw (DC 14), or they will begin to experience a flesh rot that will consume their body (thus killing them) in 1d10+2 days if they are not healed with a greater restoration spell.

Pick. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 14 (3d6 + 2) piercing damage.

The cave troll has a ranged attack that it can make as a bonus action.  Drawing rusty metal "shivs" from various places on its body, the cave troll can throw these up to 40' in distance.   Ranged Weapon Attack: +9 to hit, range 40 ft., one target. Hit: 8 (1d10 + 2) piercing damage.