This perk was originally on the Nightstalker subclass but was removed in exchange for quiver.
Perk: Gloamranger
Perk description: Unite your allies! Reduces incoming damage and buffs outgoing damage for your tethered fireteam.
This would be a pretty good support perk on an exotic.
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Another one was like Quiver, and had you shoot the tether, and 2 explosive arrows after.