Alpha Reaver

Extreme Sunlight Sensitivity. This creature makes all perception and saving throws at disadvantage in direct sunlight. It can also only take one action per turn while in direct sunlight.

Infectious Strikes. When this monster lands any attacks on a creature they must succeed on a dc 15 con save or become infected by the reaver disease.

Reaver's Disease. Any creature effected by this suffers the poisoned condition and will turn into a lesser reaver in 1d6+1 days. Any creature that dies while infected will raise as a lesser reaver at the start of its next turn.

As long as this monster is not in direct sunlight it can make 3 attacks per round. It can only bite once per round.

Bite.  When this monster has a creature grappled it will be able to bite them doing 2d6+4 Piercing and 3d6 necrotic. 

Claw Attack Melee Weapon Attack: +8 to hit, reach 5 ft., 1 target. Hit: 10 (2d6 + 4) [slashing] damage. If it lands the claw attack and hasn't already grappled a target it can forgo the damage and grapple the creature it attacked.

Embrace of Death. When a creature attempts to leave the Alpha Reavers threat range the reaver can make a contested grapple check. If it succeeds the creature is grappled and cannot move.

This monster has 2 Legendary actions.

Commanding Roar (Costs 2 Actions). The monster lets out a bellowing roar causing all nearby reavers to move their full movement and make a single attack on the closest enemy if able.

Dreadful Stare (Costs 2 Actions). If the monster can see a creature it can cause them to become overwhelmed with fear. The creature must succeed on a dc 15 wisdom save or become frightened and must use their reaction to move as far away as possible.