Hamelin

Hamelin is a guild in Elder Tale and a major villain of the Round Table arc.

Overview
Hamelin was a medium-sized guild located in Akihabara. Its policy was supposedly "mutual assistance for beginners" and recruited many of them during the Catastrophe. However, their true intention was to collect the beginners' EXP Pots and sell them to battle guilds like Black Sword Knights and Silver Sword, a plan that proved to be quite profitable.

Aside from taking their EXP Pots, the leaders of the guild also took advantage of the beginners, using them to earn Gold or ordering them around for the leaders' benefits. They ultimately did not care about their members' well-being and were not above hurting them to teach them a lesson.

Hamelin apparently disbanded after Shiroe blacklisted all of its members from using their Guild Hall and freed the beginners. With no access to their funds, equipment or even their own Guild rooms after they left the building, the members of Hamelin found it virtually impossible to live within Akihabara. As a result, they were forced to leave the city and now must fend for themselves elsewhere.

Guild Hall
Like most guilds, the Hamelin guild owns a Guild Hall of its own, a special zone for its members. Though Guild Halls are originally non-combat areas, the Guild Master adjusted the Guild Hall's setting, allowing combat in order to "manage" the beginners.

With the members of Hamelin now blacklisted, they can no longer access that zone. They were able to escape by using the  'Call of Home' spell or by killing themselves and respawning in the Cathedral. However, they cannot return to their zone afterwards.

Trivia

 * The name of the guild is an obvious reference to the Pied Piper of Hamelin. According to legend, the German town of Hamelin was plagued by rats and hired a rat-catcher, the Pied Piper. He does so using his magic pipe, but once the townspeople refused to pay him, the Pied Piper used his powers to enchant the children of the town, taking them away.
 * Shiroe, like the Pied Piper, took away all the young beginners from Hamelin due its corruption and abuse. In different ways, they are also both enchanters; Shiroe's class is literally Enchanter, while the Pied Piper used his flute to enchant the rats and children into following him.