Or maybe Glare could make Pokemon sometimes not move, like paralysis or something. And it can use Solar Beam when the sun isn't impeded and charges faster when it's super sunny, because it takes in solar energy.
Sorry to single you out, but these sorts of posts are everywhere in this thread and it's ridiculous. The flavor provided in Serperior's pokedex is already perfectly well-displayed by its movepool. Out of all the goofy dex entries (for instance, Golem can't be damaged by dynamite, which mean's Magikarp's tackle, which damages Golem, is stronger than dynamite) there's no need to stretch for strained ideas like yours. Be creative.