Blight Gnoll

Rampage. When the Gnoll reduces a creature to 0 hit points with a melee attack on its turn, the Gnoll can take a bonus action to move up to half its speed and make a bite attack.

Infectious Blight. Creatures bit by the Blighted Gnoll have a chance to be infected with the same disease as the Gnoll. The affected target must succeed a DC 12 Constitution Saving Throw. On a failed save, the creature had disadvantage on ability checks and is considered Vulnerable to all Necrotic damage. The Blight will worsen in 1d4 days if not treated, causing 25 (5d10) damage and immediately causing two points of Exhaustion. Each day the Blight is not treated the creature will take 25 (5d10) damage and a point of Exhaustion. Long Rests do not remove exhaustion and healing will only be 50% effective. The Blight can be healed through Lesser/Greater Restoration, Lay on Hands or a DC25 Medicine Check. 

Blighted Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 4 (1d4 + 2) piercing damage and 4 (1d4+2) necrotic damage. On a hit, the target must succeed a DC 12 Constitution Saving Throw of be infected with the Blighted Condition.

Spear. Melee or Ranged Weapon Attack: +6 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 6 (1d6 + 3) piercing damage, or 7 (1d8 + 3) piercing damage if used with two hands to make a melee attack.

Longbow. Ranged Weapon Attack: +6 to hit, range 150/600 ft., one target. Hit: 6 (1d8 + 2) piercing damage.

Mirewalk. As an action, the Blighted Gnoll can submerge itself in the Blighted Mire that surrounds it. It can move up to half it's movement and reemerge anywhere the Mire touches, or stay submerged until the beginning of it's next round, when it must reemerge before the end of it's turn.  It can use it's bonus action to reemerge from the mire.