Transcendent Mask design
Mask is a type of equipment, worn by all classes. Mask goes to face armor slot in character profile. Mask equipment was added in May 2018 patch the Gilded Mask.[1]
Note that slot was previously used for Alliance masks that only had visual purpose. Those were move to "Costuming" tab.
Mask are not given with other equipment upon reaching level 65, but is obtained by various methods.
As of patch v102 January 2021 mask is finally part of gear you receive as part of Apex quests. This gives highest quality Annihilation or Dark Light mask depending on class. Masks that drop from dungeons (DA) are minor upgrade since they can have additional random stats. New Kaia's Fury/Wisdom Mask was added in patch v105 in May 2021 as dungeon drops. These new masks follow Exodor gear stats changes and have physical or magical amplification values.
Note: mask equipment is completely different in console versions.
There exists Survival Mask with protective stats acquired from Red Refuge (Hard), Powerful Mask with attack stats from Guardian Legion missions, or purchased with Legendary Tokens.
Also there's Light Mask for flying enhancement from Guardian Legion missions, or purchased with Pilot's Tokens and Rider's Mask for mount improvements purchased with Warmonger Tokens.[2]
History[]
First generation of masks comes in two types, each of which have three varieties.
First type is Onset Mask which dropped in Red Refuge (Hard).
Other places to get it are Antaroth's Abyss (normal) and Dark Reach Citadel.
Second type is the Infinity Mask from DRCHM, AAHM, and Grotto of Lost Souls.
It is also possible to get masks from Leaderboard rankings, battleground boxes, Gridiron tokens and from Dreadspire (least on NA).
Third type is the Transcendent Mask which is from the Grotto hard mode and Bahaar's Sanctum. This type of mask was added in October 2018 patch 75 "Dark Reaches".[3]
Each mask type has three varieties; Powerful (power), Keen (crit factor), Bitter (crit power) and Energetic, which gives cooldown reduction (CDR). Most classes want the cdr masks. In addition masks have one random roll.
Low-end Guardian Mask was added in August 2018. It was initially drop from Demon's Wheel event dungeon and given out in EME leveling event before it was added to dungeon drop tables later. Guardian Mask has very low stats. It has +2 endurance and one random stat (non-rerollable) maximum are +6 crit factor or +3 power. Guardian Mask has no energetic version.
Exodor patch added two types of masks matching new Exodor gear: Annihilation and Dark Light masks (check article for difference of these sets). These are bought with 
Azart Tokens. 400 tokens gives box for random mask with possible random non-rollable lines. Masks are also tradeable unlike other versions.
Exodor set masks are different from older masks, they don't have defensive Endurance stats but offensive amplification stat line.
After patch 92 (April 2020) mask is part of Exodor Scout gear you'll receive as part of Awakening quests. This mask is named "Federation Supply: Guardian Mask". It is identical to older Energetic Onset Mask (and not old Guardian Mask). Onset masks also drop in Macellarius Catacombs. All dungeons moved to level 68 drop Transcendent Masks.
Bahaar's Sanctum drops special Bahaar masks, that are like Transcendent Masks, but have extra random non-rollable stat line.
Dismantling, Upgrading Masks[]
It's possible to dismantle higher masks. Ie. dismantling the Infinity Mask gives mask coupon. New mask of your choice costs four coupons. Mask Coupons cannot be stored in bank.
To upgrade Onset Mask to higher type (of same variety, like CDR mask) you need to dismantle two Infinity Masks. Guardian masks can't be upgraded.
About Cosmetics[]
Everyone doesn't like how masks look on character. Any Face Costume hides mask. There also exist Transparent Mask costume that hides mask and shows your face, if you don't like to wear glasses or something like that.