Chiton is a daemon which, while active, raises the armor of every guard by 1. Chiton normally has a duration of 3–4 turns. If multiple instances of Chiton are active at the same time, their effects stack.
Chiton is found in the Contingency Plan DLC. In the extended campaign starting from the OMNI Foundry Lab mission, an instance of Chiton is triggered at alarm level 2 in every mission, which lasts for the rest of the mission.
Chiton can be a relatively weak daemon, or a very painful one, depending on your strategy and equipment.
In high-stealth strategies based on avoiding or distracting guards, Chiton is often harmless since you aren't attacking guards anyway. If your plan is to escape from emergencies using a Cloaking Rig instead of a weapon, then Chiton doesn't matter.
In more aggressive strategies which rely on fighting, Chiton can be a problem, especially if many guards are already alerted. However, even here, Chiton is fine if you're prepared for it. If you have armor piercing weapons such as Shalem 11's Desert Wind, then you can still attack many guards. Otherwise, there are still options such as Shock Traps, Flash Grenades, Flash Packs and HoloCircuit Overloaders which deal KO damage ignoring armor.
In the extended campaign, Chiton makes weapons without armor piercing significantly less useful after day 3. Their useful life can be extended with Penetration Scanner or Piercing Scanner, but you will usually still want to replace these weapons with higher-tier versions before day 4.