Another issue translating English to English. It would be more proper to have a “more info” button sending you to a page with information on how to craft/obtain it.
If I remember correctly these imps populate in the soulforge as well as drop in keys. (glory/gem)
They are part of the regular rotation in the soulforge for Legendary troops; their appearance is not tied to the season (unlike how they appear in chests).
Sadly, most players will have to resort to the soulforge to get the imps, as the chances of pulling one are lower than pulling a mythic. Not only that, given that they don’t count towards kingdom progression, it’s hard to justify spending diamonds on them. It’d be nice if they (and the Apocalypse mythics, for that matter) get worked into some new event as reward troops, but I’m not holding my breath.