Adventure of the Blue Diamond is a Princess of Power minicomic.
Temperatures are dropping throughout Etheria; snow is falling everywhere. She-Ra enlists Bow and Double Trouble's help to investigate. Double Trouble finds Catra (who is of course behind this) in a cave where she is holding Frosta prisoner. Catra trusts DT and tells her to watch after Frosta while she is away. DT of course betrays her "friend" and notifies the others. Frosta is free, but Catra has found the Blue Diamond in the meantime, which allows her to turn Etheria into a wasteland (by shutting out the sun). Frosta freezes Catra, She-Ra cracks the diamond's outer shell with her sword and Bow shoots the inner part into the (now dark) sun with one of his arrows. The evil magic is broken.