This gigantic entity has not been given an official name in-strip. However, when it was Gil and Higgs looming over the time-frozen city of Mechanicsburg and slowly reaching for either Klaus Wulfenbach or the Take-Five Bomb he is currently holding, it was assumed by the readership that it was the first Hideous Extradimensional Being to be encountered in the story and was therefore labelled as Type 1. Of course, beauty being in the eye of the beholder, there may not be universal agreement that the being is hideous. And subsequent revelations have shown the "Type 1" to be possibly incorrect as well (see below), but it's probably simpler in this case to err on the side of inertia.by
The name was inspired by Doctor Yglyn when walking Agatha Heterodyne through her initiation ceremonies in the Red Cathedral: "Now! Are you prepared for the dark rites and twisted oaths of the Heterodynes?! [...] Some are purely ceremonial, but some utilize mysterious lost sciences to hold back hideous extradimensional beings that would ravage our world!". (Since these beings reportedly intend to ravage our world, perhaps the hideousness is in their behavior rather than their appearance.) While it is not certain that this is one of the beings described by Yglyn, it seems likely.by
Castle Heterodyne claims when someone meddles with time, as the Baron did with his device, and (after being shown the creature via remote camera, and getting the resulting spot of panicking out of the way) it estimates it will reach its target in roughly two years, when Something Bad is very likely to happen. The Castle was aware of that first fact due to Agatha's ancestor Robur Heterodyne, who discovered similar time-stopping technology three hundred years ago; it goes on to say that he and subsequent Heterodynes abandoned this power because of Robur's encounter with similar (though not identical) beings. The Castle, as is its wont when doling out information, fails to describe the beings Robur summoned in any great detail, but it later to Gil that, like the creatures whom the Castle (sketchily) describes, the Dreen also possess: 1) a very alien relationship to time; 2) hats. And, sure enough, the reader eventually that it was indeed the Dreen that Robur accidentally summoned. Given that the Dreen have been since Agatha's visit to Castle Wulfenbach, each of these two types could labelled as the Hideous Extradimensional Being Type 1, but the matter has been left up to the readers to decide for themselves..