I hope you are being facetious. If you aren't you should know it's a buggy mess and never works. To this day, i have never gotten signed up for the newsletter on Legends of Keepers.
You shouldn't take or really care about my experience or single opinion. Check the Legends of Keepers Reviews and boards and there are a decent amount of complaints about it even in the positive reviews. In that game, the content is stuff fundamental to the gameplay, with no reskins or a minor variation. Entire new monsters into already small pools of monsters. Not only were they locked behind a newsletter they were timed and would expire meaning after a certain date if you were later to the show you would never get access to that content.
It's that last part that helps explain the strange deal about their newsletter. They leverage "Fear of missing out" to further manipulate players into joining. They obnoxiously have promos and adverts for it in-game menus
The whole thing is bizarre like in school they had some class that said newsletters are very important and they got fixated on it. 90% of emails will auto-spam it anyways so I doubt it is very effective. If you wanna sour steam users quickly have them pay XX.XX for your game, log in and see a giant annoying box telling them certain heroes or exclusive monthly heroes cant be accessed in the product they paid for until they sign up for the newsletter and receive a code to enter for it. It is not how one should treat customers who paid for your product. I like them other than that one bizarre fixation they have.
Sorry for the blog. I hope you just fucking with me. I rather them have a portion of the ingame main screen real estate dedicated to them with rating adds for new upcoming content that is hyperlinked or opens stuff in steam.