Innate Spellcasting. Zuggtmoy's spellcasting ability is Charisma (spell save DC 23). She can innately cast the following spells, requiring no material components:
Legendary Resistance (4/Day). If Zuggtmoy fails a saving throw, she can choose to succeed instead. Demonic Awakening (Recharges after a Short or Long Rest). If Zuggtmoy would be reduced to 0 hit points, her current hit point total instead resets to 266 (80% of her maximum hit points) hit points, she regains any expended uses of Legendary Resistance . Additionally, she can now use the options in the "Mythic Actions" section for 1 hour. Magic Resistance. Zuggtmoy has advantage on saving throws against spells and other magical effects. Magic Weapons. Zuggtmoy's weapon attacks are magical.
Multiattack. Zuggtmoy makes three pseudopod attacks. Pseudopod. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 15 (2d8 + 6) bludgeoning damage plus 9 (2d8) poison damage. Infestation Spores (3/Day). Zuggtmoy releases spores that burst out in a cloud that fills a 20-foot-radius sphere centered on her, and it lingers for 1 minute. Any flesh-and-blood creature in the cloud when it appears, or that enters it later, must make a DC 20 Constitution saving throw. On a successful save, the creature can't be infected by these spores for 24 hours. On a failed save, the creature is infected with a disease called the spores of Zuggtmoy and also gains a random form of madness (determined by rolling on the Madness of Zuggtmoy table) that lasts until the creature is cured of the disease or dies. While infected in this way, the creature can't be reinfected, and it must repeat the saving throw at the end of every 24 hours, ending the infection on a success. On a failure, the infected creature's body is slowly taken over by fungal growth, and after three such failed saves, the creature dies and is reanimated as a spore servant if it's a type of creature that can be (see the "Myconids" entry in the Monster Manual). Mind Control Spores (Recharge 5–6). Zuggtmoy releases spores that burst out in a cloud that fills a 20-foot-radius sphere centered on her, and it lingers for 1 minute. Humanoids and beasts in the cloud when it appears, or that enter it later, must make a DC 20 Wisdom saving throw. On a successful save, the creature can't be infected by these spores for 24 hours. On a failed save, the creature is infected with a disease called the influence of Zuggtmoy for 24 hours. While infected in this way, the creature is charmed by her and can't be reinfected by these spores.
Rally Plants. Up to four plant creatures that are friendly to Zuggtmoy and that Zuggtmoy can see can use their reactions to move up to their speed and make one weapon attack. Summon Fungi. Zuggtmoy causes a gas spore or violet fungi to appear in a unoccupied space that she can she. They vanish after 1 minute.
Protective Thrall. When Zuggtmoy is hit by an attack, one creature within 5 feet of Zuggtmoy that is charmed by her must use its reaction to be hit by the attack instead.
Zuggtmoy can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. Zuggtmoy regains spent legendary actions at the start of its turn. Attack. Zuggtmoy makes one pseudopod attack. Exert Will. One creature charmed by Zuggtmoy that she can see must use its reaction to move up to its speed as she directs or to make a weapon attack against a target that she designates. If Zuggtmoy's Demonic Awakening trait has activated in the last hour they can do both.
On Initiative count 20 (losing initiative ties), Zuggtmoy can take a lair action to cause one of the following effects; she can't use the same effect two rounds in a row:
Zuggtmoy's principal lair is her palace on Shedaklah. It consists of two dozen mushrooms of pale yellow and rancid brown. These massive fungi are some of the largest in existence. They are surrounded by a field of acidic puffballs and poisonous vapors. The mushrooms themselves are all interconnected by bridges of shelf-fungi, and countless chambers have been hollowed out from within their rubbery, fibrous stalks.