Okay, this seems kind of stupid on Solomon David's part, assuming Jagganoth no-sells it due to his invulnerability (which SD knows about!). It might be more productive to use your impossible superspeed and destructive power not against the one target capable of resisting it, but against the rest of his various weapons. To be sure, an unarmed Jagganoth is still plenty dangerous as a giant indestructible wizard, but most of his techniques so far are channeled through his weapons. Ordinarily, I'd suggest chucking him into space, but teleportation seems to be one of the basic functions of the Keys, so that's less productive than it would be against other fictional juggernauts.