The only character I know with guns embedded into their arms is 400+ years in the future after everything's gone to shit. Not revealing anything, 'cause it'd be spoileeers. :V

Anti-magic cannon? No-ish, antimagic does exist with Gods, Old Gods and an upcoming thing... but cannons?

The Order of the Innocent Blade, can make mechanical Gods hundreds of meters high - can't build most guns. 

Also fighting extra terrestrial crap? When do we have aliens now? I am actually introducing aliens in a while... but they have no technology aside from a few magic properties.