Rampage. When the witherling reduces a creature to 0 hit points with a melee attack on its turn, it can take a bonus action to move up to half its speed and make a bite attack.
Burning Bones. The witherling is wreathed in flames. If a melee attack is made against it, the attacker must make a DC 15 DEX save or take 2d6 fire damage. When reduced the 0 hit points, the witherling explodes in a burst of flame. Every creature within 30 ft must make a DC 15 DEX save, or take 2d8 fire damage. This explosion is canceled out if the creature is killed by radiant damage.
Multiattack. The witherling makes two attacks: one with its bite and one with its club, or two with its club. It then makes a fire attack.
Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: d4+2 piercing damage.
Club. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: d4+2 bludgeoning damage.
Fire. Ranged Weapon Attack: +3 to hit, reach 120 ft., one target. Hit: 2d10 fire damage.
Vengeful Strike. In response to a gnoll being reduced to 0 hit points within 30 feet of the witherling, the witherling makes a melee attack.