The NPCs are divided into 5 main ranks for each faction with an additional "training" tier (T0) on the alpha islands. These ranks reflect the potential danger of engaging a robot and the possible loot that can be obtained from destroying it. The higher the rank, the higher the risk and reward.
But since NPCs differ in several aspects, it is not always a given that a T3 NPC robot will always be easier than a T4 NPC robot.
Two additional NPC classes, so called elite and observer, also exist.
The following table gives an overview of the elite NPC prefixes for each faction.
These rare NPCs have a chance to drop better than normal loot.
Observers are more powerful than any other NPCs. On Alpha islands you will encounter grand observers which reflect T4 equipped robots with maximized extensions. On Beta and Gamma islands superior observer can be found. These robots have a higher level of skill than T4 equipped robots with maximized extensions.
NPCs robots use their racial weapons and are weak to their opposite faction's weapons. The table below details the damage they deal and which type of damage they are weak to.