A parabatai is a pair of Nephilim warriors who fight together as lifelong partners, bound together by oath, regardless of their gender. Their bond is not reflected only in their closeness and willingness to lay down their lives for one another, but also in oath—one sworn in front of the Council.

Not all Shadowhunters are required to have parabatai; it is actually less common to have them. A Shadowhunter has only eighteen years to find and choose a parabatai; once older than that, the ritual is no longer open to the Shadowhunter.