bio lab
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Ragnarok Online's most famous dungeon, added in 2005 in Episode 10.2. Compared to most other dungeons featuring various monsters, the Bio Labs had enemies with names who mirrored the player classes. It also was much more difficult than most of the other dungeons at its level and had valuable drops. All of these factors made the Bio Labs one of the most popular spots to grind for levels and the rare monster cards.
For tagging purposes, use this when the characters are shown with their characteristic aura (such as Danbooru post #4320593), or the laboratory ruins are present.
In 2017, the enemies on the third floor received a webtoon, viewable here: Requiem For The Lost
For a list of the enemies, see the List of Ragnarok Online Characters.