There are three Onion Helms. Peregrines which is done by getting deaspected crystals. Red Onion Helm, which is a reward from AV. And Onion Helm which you get from the CE if you bought it the first week (or maybe any CE). You can get the gear by doing the level 20 faction levees. It can be given either through the awards of the levee or in the chest at the end.