Marvel Lad, who also calls himself Legionnaire Lemon, competes for membership in Adventure 305 (Feb 63), another Jerry Siegel tale.
Open auditions are held again, and it becomes a regular feature of Legion tales, in which rejected applicants are briefly introduced, many of whom would return, sometimes decades later. This issue introduces Antennae Boy, who is not seen again until the mid-80s.
The focus of the story is on Marvel Lad, who displays a staggering range of powers, and even invents an anti-gravity metal as part of his initiation. More significantly, he battles and defeats a Sun-Eater. This creature bears little resemblance to the more deadly version that would be seen a few years down the road, but still is a challenge.
In the end he is revealed as Mon-El, a complete surprise for anyone who cannot reverse the letters in Lemon. Brainiac 5 developed a cure for his lead poisoning and released him from the Phantom Zone. As they waited to see if it would function on a long term basis, Mon-El came up with the Marvel Lad identity to have some fun with the team he had joined months earlier, without being able to participate.
It`s a bit sad seeing that Jax-Ur is still in the Phantom Zone, more than a thousand years after the destruction of Krypton. As evil as he is, being sentenced to eternal punishment is a bit much.