This is based on the new gate nodes introduced in the Operation Isomer event. The gates in the game can be open and close by the players which allows them to let their echelons or the enemy to enter another node or block them if they choose to do so and if the player accidentally closes the gate while their echelon is still in there, it will cause a 25% damage on their health.
However, instead of being use as a road block against enemy units like the developers wanted, players discovered that enemy units can also be damaged by the gate, even armoured units and bosses! Que players luring enemy units to the gate and repeatedly opening and closing to dwindled the enemy's health to the point it's so low, they can send their echelons to easily finish off the enemy.
