I'd like to know if this is a bug.

[Shadow_Lord]

I wanted to buy Persephia with a 7-star ticket but it’s not showing up; instead, Onyx appears twice.

[Shadow_Lord]

[Shadow_Lord]

[Dev_VKC]

It was indeed an error. Persephia was mistakenly replaced by Onyxia. We’ll be fixing it shortly.
Thank you for reporting it!

[Exu]

Before you do it, I’d strongly advise against spending 3 tickets on Persephia, she’s a Gold Egg mythic that’s more available than new featured mythics!