While the Onyx Sentinel is designed to handle threats greater than the flood (meddlers as the monitor refers to) the Enforcers are easier to produce, stronger than standard regular sentinels and employ better anti-personal and anti-vehicle weapons, generally good against vehicles from what I've seen. They fire a crystal like needler which was what the covenant reverse engineered their needler from, and it lobs mortars like small missiles at enemies, great against flood. If a player manages to shoot off the needler and missiles, it does fire an invisible bluish beam similar to a sentinel major but more powerful. Since this is difficult to do, Bungie left out the use of it and its visual files, but if you can manage to shoot off the other weapons, it forces the program to revery to it.
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Quoting DEATH BOY
how is the beam invisible if u can see it
well be sure your not talking about the red needler things that it shoots or the rockets it throws overhead at you. I myself have tried shooting off those weapons o see the beam with no luck, it usually blows up first but some have probably with mods gotten it to stop using the red guns and the arching grenade rockets and said they are hit with a beam that only the player being attacked can see.