Telepathic Bond. The toad ignores the range restriction on its telepathy when communicating with a creature it has charmed. The two don't even need to be on the same plane of existence.

Claw. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 6 (3d6 + 3) slashing damage.

Charm. One humanoid Yumzo can see within 30 feet of it must succeed on a DC 15 Wisdom saving throw or be magically charmed for 1 day. The charmed target obeys the toad's verbal or telepathic commands. If the target suffers any harm command, it can repeat the saving throw, ending the effect on a success. If the target successfully saves against the effect, or if the effect on it ends, the target is immune to Yumzo's Charm for the next 24 hours.

The toad can have only one target charmed at a time. If it charms another, the effect on the previous target ends.

Draining Kiss. The frog kisses a creature charmed by it or a willing creature. The target must make a DC 15 Constitution saving throw against this magic, taking 32 (5d10 + 5) psychic damage on a failed save, or half as much damage on a successful one. The target's hit point maximum is reduced by an amount equal to the damage taken. This reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0.

Enter the description for how mythic actions work for your monster here.

Mythic Action Name (Costs # Actions).  Can inhabit a person's mind and control their thoughts.