Evilseed appears to be an avatar of plant-life, though not in its life-sustaining side. Rather, he embodies the aggressive side of the plant kingdom, growing for growing's sake, and not concerned about what it displaces as it does so. In Evilseed's case, this natural tendency of any living species is made into an active desire for conquest. Notably, he attacks both sides in the Skeletor/He-Man conflict, and both sides at first blame the other for the incessant attacks. While the hero and villain forced to work together can be an overused cliche, it was in fact rare for MOTU, and in this case, the threat was very real and very total. Most and at one point close to all of the opposing warriors were entirely disabled by Evilseed. His design seemed reminiscent of something from the Don Bluth animation studios.
Evilseed began by giving seeds to farmers that he promised would grow even in bad soil. While true to his word, the vines they produced quickly went out of anyone's control but Evilseed's, and before long they infested the planet. Even mystical viewing portals like those used by the Sorceress and Skeletor were not immune to vines springing out of them. At first rejecting He-Man's call for a truce, an overwhelmed Skeletor quickly relented. Upon entering Castle Grayskull, Skeletor at first tried to drain the power from the Castle and the Sorceress, but was forced by He-Man to be mindful of the greater threat. As the remaining forces were taken apart trying to get to Evilseed's lair, He-Man gathered a huge block of ice, and as it flew towards Evilseed, Skeletor blasted it to tiny pieces, raining snow on Evilseed and his vines, ultimately killing them both by freezing. This seemed to be enough to permanently destroy Evilseed, who did not appear again in the original series.
In the 2002 series, he was more like a humanoid Biollante, and was freed by Orko, who thought he was the heroic Moss Man. Moss Man, a much more fully realized (and likely a cooler) character in the 2002 series, was now more like a mix of Swamp Thing and Batman, and had opposed Evilseed as long as there had been plant life on Eternia, and their intense rivalry did not end with Evilseed's defeat in this episode. When freed again, Evilseed was forced to serve Skeletor, but once more Moss Man came to the aid of his allies.
No version of Evilseed has been made into an action figure.