Trion (トリオン Torion?) is a biological power source, or energy, that resides within every living human, and possibly in other life forms as well.[BBF Q176] This energy provides power for a Trigger's various abilities and functions. Trion is also a term that plays a major role in the world of World Trigger.
Trion is produced by an invisible organ, better known as the "trion gland". It is not known of in the human world, but every human possesses this organ, located next to their heart. Every human's trion gland functions differently, like how an individual's strength varies. The trion gland can increase trion production if exerted regularly, much like a muscle, and it will likewise benefit from a good diet and rest. After the age of 20, however, it stops developing and starts to decay if not exerted, meaning it is best to train Trigger users while they are young. A high trion value can allow an individual to develop one or, in exceptionally rare cases, multiple Side Effects, and plays a crucial part in the creation of a Black Trigger.
The functions of the trion gland are directly connected to a Trigger's power. If the same Trigger is used by a different person, differences will appear concerning their trion values. While using a Trigger, the user will go into a trion Body, which is their body made fully of trion. Their normal body goes into the Trigger holder. They squirt out gas instead of blood (green sparkles in the anime). If there is a signficant amount of trion loss, the body will revert to their normal body, or in the case of Border personnel above C-Class and below S-Class, will initiate Bail Out. The regeneration time is proportional to the amount of trion used; the greater the trion expenditure, the longer the regeneration time.
Usually people with low trion levels display no capability of using Triggers, thus they are mainly captured by Neighbors for their trion producing gland.
They are capable of using triggers if they have to, but most are not recruited by the Border Guard because they could never use triggers effectively, or very long.
Users displaying high levels of trion make up most of the Border's upper ranked agents, able to carry out and enlist for missions in order to protect Mikado City from the swarming Neighbors.
Rare individuals with immense levels of trion are capable of inhuman feats, such as measuring towards Black Trigger levels. These users are usually the top A-Rank and even S-Rank agents of Border.
Trion differs among individuals also due to its quality. How exactly this property affects it is unclear, but it has been suggested that higher-quality trion makes trion manipulation easier, which in turn improves the accuracy of one's control over their Triggers.