Seven Member Party

Seven Member Party is the tentative name referring to a group of seven people who were tasked with subduing the tree monster in the Great Forest of Tob.

Background
According to Pinison Pol Perlia, it comprises of three young humans, one tall person (presumably a Giant), one old human, one person with wings, and one dwarf. At some point in time, they came across Zy'tl Q'ae, a massive tree monster and tried to defeat it in battle. Unable to completely kill off the massive tree monster for good, they have chosen to seal it away instead. While successful in preventing further destruction than where it is at now, the group made a promise to Pinison that they would one day come back and defeat Zy'tl Q'ae once and for all.

The Sealed Evil Tree Arc
With the inevitable awakening of Zy'tl Q'ae looming near, Pinison was waiting for the return of the seven-member party to come and stop it. She would later explain to Ainz and Aura about her past experience where the Seven Member Party encounter the monster in a battle and how they deal with it. Ainz promised Pinison that he and his group will be the ones to defeat it if possible; if not, he will evacuate the dryad and go search for the Seven Member Party to handle the matter. Fortunately, Ainz's mission of combating Zy'tl Q'ae was a success thanks to the efforts of the Floor Guardians who aided him.

Strength
The Seven Member Party was apparently strong enough to give the level 80-85 Zy'tl Q'ae a good beating. However, Pinison noted they had a real struggle fighting at least only a part of its body.

Trivia

 * The leader of the Seven Member Party was the person who gave the tree creature its name, Zy'tl Q'ae.