Arcs (or Orcs) are a powerful type of enemy seen in Phoenotopia and Phoenotopia Awakening. Along with Harpies, they're one of the breeds of mutant supersoldiers that were created during the Great War as a prototype for the Phoenix Weapons; as such, they are strong fighters and somewhat difficult to deal with.
Arcs are bulky humanoids that are mostly bald and have sparse clothing. All enemy Arcs encountered in the game have green skin, though other colors have been shown in friendlier Arcs.
Arcs are among the rarest enemies in the game, appearing sparsely in the Phoenix Lab, having been cryogenically preserved there, and as regular enemies in the Forgotten Forest. In terms of attacks, Arcs combine the abilities of both the red and blue Desert Bandits. This means they can use close-ranged attacks with their axes and throw them as well.
A tribe of peaceful Arcs resides in the Hidden Village, functioning as NPCs that Gale can interact with. Unlike the generic enemy Arcs, these ones are very docile and welcoming towards Gale, as they had previously been befriended by Grasso, and then later by Fran and her team of researchers. These Arcs show a wider variety of skin colors.
Arcs will return in the remake as both enemies and NPCs. In this game, they are called Trolls and are said to have the ability to turn into stone, just like actual trolls. 
- As stated by the game's creator, the Arcs were originally going to be the main antagonists of Phoenotopia, being led by one particularly brainy Arc. Obviously, the final product has come a long way since then.
- One of the Arcs at Hidden Village states that they have their own language but use the human language as a meeting ground with the Harpies, implying that the Harpies also have their own language as well.
- Interestingly, when an Arc is defeated, his body flies off the screen instead of disappearing in a puff of purple smoke like most other enemies. Arcs are the only type of enemies to do this when killed.