I didn't wanna put too much in the TL note, so I'll go over it a bit more here in case anyone's curious.

Memorial Lobbies in Blue Archive are special Live 2D scenes that 2-3☆ characters receive that relate to their bond stories. However, as of the latest update, Serina—who was a 1☆ added on launch—has received a Memorial Lobby that's unlocked on her 4th bond story; thus, making her the very first 1☆ to ever receive one in the game (albeit voiceless).

A very well deserved one too imo, since she's helped so many Senseis especially in PVP and on the Hieronymus raid ^v^