PSE (Photon Sensitive Effect) is a mechanic that only appears in Combat Sectors. PSE is represented by a meter that appears beside the minimap which shows the current level of the PSE. This will increase or decrease randomly in level by defeating enemies in the combat sector and by successfully completing trials. The PSE Burst can only start after a Trial. PSE levels will not decrease over time.
As the level goes up, the appearance rate of rare enemies will increase, and when it reaches the maximum, a PSE Burst will occur. PSE levels are affected by weather conditions, such as thunderstorms. During special weather conditions, the PSE levels in all applicable PSE Burst regions will always be at a minimum of 4 levels. This effect will not subside after completing a PSE Climax until the thunderstorm is over.
During the PSE Burst, the PSE meter will slowly drain, representing the amount of time the PSE Burst is active for. Many enemies will appear at a special rainbow "E" marker during the PSE Burst. Once the PSE meter empties, a PSE Burst Climax will occur, and a boss with the Silver or Golden variant will appear.
Completing a Chaos Trial, which is when two trials occur at the same time, will guarantee an increase to the PSE gauge by 1 bar. There is a chance that when completing a Chaos Trial at 3 bars, the PSE gauge will increase by 2 bars, resulting in a PSE Burst.
Defeating enemies in an area targeted with a yellow "E" marker will have a 10% chance to raise the PSE gauge by 1 bar, while also having a 5% chance to decrease the PSE gauge by 1 bar. Defeating enemies in an area that is not targeted with a yellow "E" marker will have a 10% chance to raise the PSE gauge by 1 bar, but has a 10% chance to decrease the PSE gauge by 1 bar. Yellow "E" markers will switch to another group of enemies once 80% of the enemies in the previous "E" marker have been defeated.
Killing any enemy in the room will have a 5% chance to begin an Emergency Trial. Completing an Emergency Trial at 4 PSE gauge levels will have a 95% chance to increase the PSE gauge by 1 bar, resulting in a PSE Burst, while having a 5% chance to decrease the PSE gauge by 1 bar. The failure of an Emergency Trial has no bearing on the PSE gauge levels.
The PSE gauge does not decrease randomly over time, and is only affected by the completion of Trials or by defeating enemies. Once 5 minutes have elapsed, the PSE gauge in a given room will not decrease under any circumstances, provided the original host of the room does not leave the area. The host is classified as the player who was the first to join the area. If the first host has left the room, another host will be selected at random. The time that prevents the PSE gauge from decreasing will reset once the host has left the room, or when a PSE Burst has successfully occurred.
The specifications presented are from the results of player conducted observations regarding the PSE mechanic, and may not act as conclusive evidence regarding the PSE mechanic.
In Rank 3 Combat Sectors, after defeating the boss that spawns at the end of the PSE Burst, there is a rare chance that another PSE Burst will occur, which is known as a PSE Encore. PSE Encores cannot be chained, which means another PSE Encore cannot occur after the subsequent PSE Encore has been completed.