The Hoffman Ruins are a location based on a island in the north-east area of the world map.
The ruins are first visited when Claude wins runner-up at the Lacour Tournament of Arms and finally earns an audience with the King of Lacour, who then sends Claude and his party, as well as Leon, Lacour's head scientist, to obtain a rare mineral (Energy Stone) for the Lacour Hope, a superweapon which was built with the intention to stop the Monster Horde created by the Sorcery Globe.
When this quest is given (not having any choice), Leon, a spellcaster, just like Celine, accompanies you. If Claude is the main protagonist, at the end of the quest, you can choose whether to keep Leon in your party or not.
In another case, if you have seen the Private Action in Arlia with Opera in the Sacred Forest/Shingo Forest (the spaceship which falls in the forest), before escaping from the ruins, a scene begins, where you can recruit Ernest Raviede.
In the ruins, be careful. If you aren't prepared enough, the monsters, some of which can petrify and stone your party, and the many roads can be hard for your party. You can obtain items on the way, which can help you. At the end, a save point awaits you for a boss battle.