This magical creature is said to systemize and store all Thunder-related knowledge that Metal Units can hold within them. They are good listeners, which make them very well-liked among the talkative Metal species. They seem to enjoy listening and give exaggerated responses, but appear to forget everything a couple of hours later. They are more than happy to listen to the same story repeatedly, but they fail to remember the important facts, therefore it is believed that it's impossible for them to keep promises.
Thunder Crystals are best used as an ingredient for fusion, providing a base of 151,524 XP. When fused with Thunder element units, it grants 227,286 XP, not including Great Success (x1.5) or Super Success (x2). The unit sells for 150,000 Zel.