From Halopedia, the Halo wiki
A plasma gyve, also called a restraint generator, is a piece of technology used by the Banished to secure prisoners until they can be taken to a more permanent detention facility. The technology is similar to an energy shackle, except it can be used to restrain multiple prisoners. When activated, the plasma gyve binds its prisoners with searingly hot tendrils that force its captives into submission. In addition to keeping prisoners restrained, the plasma gyve also serves as a lure, drawing enemies who seek to liberate their allies into a deadly trap.
During the Battle for Zeta Halo, the Banished used multiple plasma gyves to keep their human POWs tied up before sending them off to the Tower for interrogation or the House of Reckoning for execution.
In Halo Infinite, captive marines tied to plasma gyves are immune to damage until the player frees them by destroying the gyve. Once freed, the marines will automatically be equipped with MK50 Sidekicks, though they will typically trade them for more powerful weapons given the opportunity.
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