Original Filmation animation cel from the He-Man transformation sequence used across the 130-episode 1983-1985 run. The sequence — Adam raising the sword, the lightning crash, the transformation into He-Man — is one of the most-reused animation sequences in 1980s cartoon history.
Catalogue source: heman.fandom.com (CC BY-SA 3.0) and the relevant studio archive.
Image: Filmation series frame, via Wiki Grayskull (fair use).