The demodands, also called the gehreleths, are the fiends native to the Tarterian Depths of Carceri. They have no stake in the blood war and have barely any society to speak of. They don't make deals, they don't want your soul, and they won't imbue you with powers. They exist soley to destroy and cause suffering.
There's not a lot of official art of these guys, so I repeat images a lot.
0:00 Intro
1:07 Pronunciation Guide
2:32 Description
5:08 Origin
8:00 Hierarchy
16:54 Abilities
20:05 Obisidan Triangles
20:57 Destruction
21:56 Physiology
23:24 Society
24:52 Language
25:13 Summoning
27:01 Outro
Sources:
Monster Manual II 1st edition 33-34
Planes of Conflict “Liber Malevolentiae” 12
Planescape Monstrous Compednium Appendix I 42-45
Faces of Evil: the Fiends 82-87
Fiend Folio 3rd edition 42-45
Planescape: Adventurers in the Multiverse “Morte’s Planar Parade” 26-27
Minsc and Boo’s Journal of Villainy 135-137