NPC, by definition, are Non-Player Controlled objects. all of them are hostile and killing them gives cel, helix and experience points. Though all are hostile, not all are aggressive, so you can bypass one without being attacked. The general rule is that NPC of level 30 or higher are aggressive, and NPC of level 50 or higher will not only attack but will probably chase you e.g. the Kallishor and Arkatos. But there are exceptions. I have run into a level 80 boss from the Kataan family (strangely, it is called the BOSS: Incubus), but it did not attack me. Another time it was the level 30 BOSS: Chelone. that was from the grindel family, and it did not attack until I lowered it's health to about 30%. Unfortunately, some Fungari and Gefion arrived on the scene and I had to retreat to Thalys.
Deepolis has a rather puzzling feature. There are NPC's with the same sprite (they look the same) but are of totally different level and therefore players will have nasty surprises. For example, most of the zone 1 NPCs have a zone 9 counterpart, which is far more powerful and harder to kill, though they give better awards, the lynx and kataan are pretty weak, but their relative, the skiach is a force to be reckoned with (for newer players or players not willing to use good ammunition). However, in zone 10, the Aranka and Rex share the same image, and it doesn't really matter because, when NPC's are level 70+, a difference of 3 will not matter (Aranka level 72 and Rex level 75).
NPC's slowly become more powerful as the Zone number increases, but zone 10 NPC suddenly become far more powerful than Zone 9 NPC, doing twice as much damage and about twice as fast.
List of NPCs with pages dedicated. They are listed in groups because they share the same image. Non hyperlinked ones are under construction. Such group vary in diversity.
-Ventes group- Ventes
-Kataan group- Kataan, Lynx and Skiach,
-Konix group- Konix, Caryer, Glypher, Elope, Gefion and Oplus
-Devon group- Devon, Fungari and Zipran
-Mordant group- Mordant, Grindel, Morph, Tisroc and Orcus
-Adamai group- Adamai and Kaupus
-Hondas group- Hondas and Kumar
-Araktos group- Araktos
-Branka group- Branka, Hollow, Zipran and Lokum
-Colossus group- Colossus and Poi
-Mythra group- Mythra
-Moomba group-Moomba, Fungus and Valmorus
-Bentu group- Bentu, Wombat and Murlov
-Taiman group- Taiman and Mantakor
-Kallish group- Kallish,
-Crusta group- Crusta
-Fira group- Fira
-Hexalon group- Hexalon and Giganto
-Makar group- Makar and Exoz
-Astatine group- Astatine, Incubus and Vryll
-Aranka group- Aranka, Rex and Malum