For I am — Blastaar! King of a limitless domain — emperor of all existence! Beside my power, all else is as nothingness! Yey — cosmic monarch though I be — I have been felled by the foulest of fates! Where is there one who would challenge my majesty? Their legions are few — their fortunes are feeble! Condemned I am by cruel conspirators who fly the vapid flag of what they would call decency and justice — condemned by them to roam the endless wilderness of negative space.
He carries on like that for two whole pages (and for every single panel he's in), with nary an editorial note, but there's a clue there (negative space). In short: he's a particularly pretentious Fantastic Four fiend.
Jean is testing a machine left behind by Xavier, which goes wrong and somehow causes Blastaar to be summoned to the mansion (at least, I think it's the mansion - it's never clear. It's also not obvious why they have suddenly been allowed to reform. Not the first time that they've forgotten why a status quo changed happened though - see Mimic being sacked after blackmailing his way onto the team). They fight and defeat him, through teamwork! Jean here comes up with the plan, to have Bobby make ice statues and then have them be propelled by her, which is quite novel.
The art for this issue is by Barry Windsor-Smith (credited as Barry Smith), who only did this single issue on X-Men, but would go on to great things. Like Jim Steranko's couple of issues, it feels very different to the Kirby/Roth/Heck style. It's bigger and more detailed, people are tightly framed and often clipped by the boundaries. Lots of pages are a simple 4-panel layout, with the maximum being 6 panels, and the speech and thought bubbles happily go over the edges. Smith was all of 20 when he drew this! Astonishing...