Winterbite is the first heavy exotic glaive and is acquired from completing the special quest "Strider" offered by Quinn in Lightfall! You must have already completed any version of the Lightfall campaign to have access to this quest.
Winterbite is a HEAVY exotic glaive that is STASIS damage.
Big Frigid Glaive
Fires a large ball of energy that locks onto nearby targets and freezes them
You must be 1750+ Light Level
You must own the Lightfall DLC and have already completed the campaign