You Belong to the Song

Unknown level, Unknown school

• Casting time: 1 Bonus action
• Range: 60 feet
• Components: Unknown
• Duration: 1 minute

The Piper targets one Humanoid within 60 feet, which makes a DC 17 Wisdom saving throw. On a failed save, it becomes Dominated by the Piper for 1 minute. He can have only one creature Dominated this way at a time. While Dominated, the creature:

• Cannot willingly attack the Piper.
• Considers the Piper someone it must protect.
• Can attack creatures threatening the Piper.
• Attempts to remain within 30 feet of the Piper.
• Can use its Reaction to move up to half its Speed toward anyone who attacks the Piper.

The creature repeats the save whenever it takes damage and at the end of each of its turns. Once a creature has been Dominated by this ability, it cannot be Dominated by it again for the rest of the encounter. If the Piper Dominates another creature, the previous effect immediately ends.

In 16-Killing The Piper

Same effect at DC 20. While Dominated, the creature:

• Can’t attack the Piper.
• Defends the Piper.
• May attack creatures threatening the Piper.
• Attempts to remain within 30 feet of him.
• Can use its Reaction to move toward creatures attacking the Piper.

The target repeats the save at the end of each of its turns and whenever it takes damage. Once the effect ends, that creature is immune to You Belong to the Song for the rest of the encounter.

Sources

Homebrew. An ability of The Piper, from the fights in 14-The Piper and 16-Killing The Piper.