Two-Headed. The abyssal wurm has Advantage on Initiative checks.

Legendary Resistance (3/Day). If the abyssal wurm fails a saving throw, it can choose to succeed instead.

Reactive Heads. The abyssal wurm has one additional Reaction that can be used only for Opportunity Attacks.

Wakeful. While the abyssal wurm sleeps, at least one of its heads is awake.

Multiattack. The abyssal wyrm makes two Bite attacks (one of each damage type).

Bite. Melee Attack Roll: +14, reach 10 ft. Hit: 16 (2d8 + 7) Piercing damage plus 18 (4d8) Fire or Cold damage.

Elemental Breath (Recharge 5–6). Constitution Saving Throw: DC 21, each creature in a 30-foot Cone. Failure: 39 (6d12) Fire or Cold damage. Success: Half damage.

Elemental Jump. The abyssal wurm teleports 30 feet to a space it can see.

Legendary Action Uses: 3. Immediately after another creature’s turn, the abyssal wurm can expend a use to take one of the following actions. The abyssal wurm regains all expended uses at the start of each of its turns.

Suicidal Presence. The abyssal wurm casts Dominate Person, requiring no Material components and using Charisma as the spellcasting ability (spell save DC 21). The abyssal wurm can’t take this action again until the start of its next turn.

Sapping Aura. Charisma Saving Throw: DC 21, each creature in a 10-ft. Emanation. Failure: The target has Disadvantage on attack rolls against the abyssal wurm until the end of the target's next turn. Success or Failure: The abyssal wurm can’t take this action again until the start of its next turn.

Abyssal Transport. The abyssal wurm uses Elemental Jump feet and makes one Bite attack.