The Devilfoil Mask in is a helmet with a peculiar, almost reptilian look, but has some important uses that players should know about once these masks are found. There are four masks to be found with relative ease, and they are perfect for party builds that focus on strength instead of magic. If a player instead favors spells over melee combat, these masks have a backup use case that can equip players with powerful bombs later in the game.
If they have not already, players will first need to enter the Underdark, more specifically the Grymforge location that is home to many side quests. Gekh Coal's missing boots quest will grant entry to the Grymforge with minimal fighting, and potentially net players some useful armor if they do return the boots to Sergeant Thrinn.
Alternatively, defeating Gekh's cohort in the Decrepit Village also grants access to the Grymforge boat and completes the «Defeat the Duergar Intruders» quest, but can be difficult due to his allies' access to invisibility and necromancy spells.
Once inside the Grymforge, the Devilfoil Masks can be found in four locations, primarily in the Abandoned Refuge region:
Devilfoil Masks have two main purposes, the first of which is equipping the item itself. While wearing a mask, the wearer obtains the Infernal Legion passive, which grants +1 to Strength and -1 to Intelligence, Wisdom, and Charisma while within a 20-meter radius of another Devilfoil Mask wearer (up to +3/-3). This is beneficial for Strength-oriented characters, such as Karlach and Lae'zel, but is not recommended for magic users like Gale and Shadowheart. If the player's entire party is built around Strength, however, having everyone wear Devilfoil Masks and attack the same enemy can quickly take down strong foes.
The masks' secondary use is introduced in Act II, when the player reaches the Last Light Inn in the Shadow-Cursed Lands. The infernal mechanic Dammon can be found here, who can craft Orthon Explosives if given Devilfoil Masks. This
Read more on screenrant.com