From the Wikipedia entry on
slaad:
[SBLOCK=Xanxost]Xanxost is a blue slaad with a penchant for exploring the planes, explaining their secrets to everyone interested, and eating whatever he can catch, particularly mephits. He appears as a character in the Planescape accessories
Faces of Evil: The Fiends and
The Inner Planes. Both of these books are written as if they were created by someone within the Planescape setting, and within that writing style, both books have an 'editor' who collected the investigations and opinions of various planar creatures on the topic at hand. Xanxost is one such character. "Though his mannerisms are often odd, his information is always reliable".
In
Faces of Evil he is one of the 'authors' of the section on tanar'ri, and in
The Inner Planes he 'wrote' the section on the Quasielemental Plane of Steam. Xanxost seems less chaotic than other slaadi in that he can write a mostly coherent piece of text, though his nature still shows through in his writing style, with many wanderings off-topic (mostly to the subject of food), repetitions of earlier remarks, and a seeming inability to count. Xanxost is referred to as "it" in
Faces of Evil, which makes some sense given the unusual nature of slaadi reproduction, but as "he" in
The Inner Planes.
[/SBLOCK]I just needed the name of a fairly-well known slaad, and I was a fan of Xanxost back in 2e.