Panel from Fantastic Four (1961 series) #47 (February 1966), script by Stan Lee, pencils by Jack Kirby, inks by Joe Sinnott, colors by Stan Goldberg, letters by Artie Simek
Why, he's even mad enough to be firing up the
How powerful is the Atmo-Gun? So powerful it makes the Earth glow in the dark. (Note: For best effect, first expose Earth to bright light, then take Earth into hall closet.)
Maximus' Atmo-Gun manipulates the atmosphere by exciting it (probably by showin' it photos of Kelly Rowland) until the very ground shakes with massive earthquakes! Or, as they probably should be technically called, atmospherequakes. It even makes the Attilan Chamber of Commerce crash and collapse! OH THE INHUMANITY! All those tourist pamphlets, gone!
Panels from Fantastic Four (1961 series) #48 (March 1966), plot and script by Stan Lee, plot and pencils by Jack Kirby, inks by Joe Sinnott, colors by Stan Goldberg, letters by Artie Simek
Here's an external shot of the Atmo-Gun that doesn't look much like the view we saw above, so I'd like to propose that the machine seen in FF #47 was the underground control module and this is the above-ground atmospheric manipulator. Either that or Jack didn't keep a reference copy for drawing its second appearance.
Maximus, as befits any nutty, wacky, way-out criminal super-genius with a hatred of his brother (see also: Loki, Grim Reaper, Fat Freddy Freekowtski), taunts Black Bolt with the sort of expository dialogue that made Goldfinger such a popular name in motion picture history.
To which Black Bolt replies, succinctly:
Which only spurs Maximus to go reverse the polarity and erect an impenetrable Negative Zone (not to be confused with the anti-matter universe ruled by Annihilus, or the corner that Sue Storm makes her brother sit in when he gets into a fight with Ben) around Attilan, home of the Inhumans! Yes, it's a giant machine with a big-ass fist-grippin' handle and when you switch it it goes "click!" Human–computer interaction at its finest!
You know, for a super-villain, Maximus' dentistry is impeccable. That's what happens when you brush with new improved Terrigen with Fluoride™!
And nobody ever saw Attilan, ever again. Until Black Bolt, under the influence of too many Bartles & Jaymes wine coolers, crashed it into the Hudson River.
Edited on 03/09/14 to insert this addition:
Maximus' Atmo-Gun is also seen in the miniseries Fantastic Four: Fireworks, although this isn't a separate appearance: FFF is one of the short-lived "Marvel Remix" series, retelling the first Inhumans story, focusing on the relationship of Crystal and the Human Torch, which is one of the few pairings in the Marvel Universe that I wished woulda happened. (Still could, for that matter!) It also, of course, spotlighted the Atmo-Gun!
Panels from Fantastic Four: Fireworks #2 (February 1999), script by Gerard Jones, pencils by Jeff Johnson, inks by Mark Pennington, colors by Richard Horie and Tanya Horie, letters by Richard Starkings and Albert Deschesne
Fireworks shows us a little more detail on the effects of reversing the polarity (©1963 BBC) of the Atmo-Gun, creating an impenetrable "Negative Zone" barrier surrounding Attilan (not to be confused with Reed's Negative Zone portal from the Baxter Building to the antimatter universe of Annihilus).
As well as showing the tragic result: Crystal is separated from Johnny forever (well, at least until FF #59).
Oh, why must I be a Fantastic Teenager in love?