User blog comment:SafeBat/What happens after you capture a monster?/@comment-4820236-20120523202922/@comment-4543229-20120523204959

I do think some of the captured monsters are killed. The guild does need materials. Others may be used for research. And others kept alive.

About pets: As of now, no big monster has been shown as a pet. We have seen Aptonoths, Popos, or the Halks from Frontier, but no big wyvern. I think those just can not be tamed. They can be trapped, kept alive in cages maybe, so they can be used in arena quests.