Three individuals performing a united Heart Hands pose. A legendary technique said to hold power beyond human comprehension.
All three characters must contribute to the same heart for it to be considered a heart hands "trio", either by each forming part of the heart or by overlapping a Heart Hands over a Heart Hands Duo (post #3369955).
If three characters are forming multiple sets of linked Heart Hands Duos, it's a Heart Hands Duo Chain instead.