Fel crystals, also known as demonic crystals, are floating crystals that are used to imprison and store demonic energies or entities.
The blood elves notably enslaved the fel by imprisoning demons, which they used to maintain their architectural structures. As of the Invasion of Pandaria, the fel crystals of Quel'Thalas seem to be gone or depleted of their imprisoned demons, as Grand Magister Rommath states that the crystals were "once" used to enslave demonic energy.
- Burning Crystal - Eversong Woods
- Fel Crystal Prism - Blade's Edge Mountains
- Crystal Prison - Shadowmoon Valley
- Fel Crystal - Magisters' Terrace
- Fel Crystal - Frostfire Ridge
- Burning Resonator - Talador
- Crystallized Fel Essence - Tanaan Jungle
- Doom Fortress Stabilizer - Mardum, the Shattered Abyss
- Spire Stabilizer - Mardum, the Shattered Abyss
- Arcing Fel Crystal - Legion Invasions
- Fel Energy Crystal - Legion Invasions
- Protected Fel Crystal - Legion Invasions
- Anchoring Crystal - Broken Shore
- Felsoul Shard - Suramar
- Soul Coffer - Krokuun
- When the blood elves in Quel'Thalas suffered from lack of magic, they sucked it from small crystals called mana crystals. At least one crystal, which Lor'themar Theron sent through Halduron Brightwing to Lady Liadrin when she was living in the Ghostlands, was described as green. Whether this means that the crystal was fel is unclear. Rommath too wore a green-colored amulet, yet its power was described to be arcane in nature. The relation, if any, between the novella's crystals and these is unclear.
A cluster of Burning Crystals.
The blood elves use demonic energy to maintain their architectural structures.
Blue crystals in ancient Quel'Thalas from World of Warcraft: Chronicle Volume 1.
- The crystals of Sunstrider Isle, called Burning Crystals, may be fel crystals.
- The Sunwell Trilogy manga's depiction of crystals that look like fel crystals of current day existing since before the Scourge invasion of Quel'Thalas may be not canon, as the blood elves did not turn to using demonic energy until long after Arthas' attack. The crystals powering Silvermoon City's magics were depicted as blue in World of Warcraft: Chronicle Volume 1 and it is possible that the blood elves substituted the powering of these crystals with demonic fel energy, a fact not made clear in the game, while the crystals themselves were already there long before. This would make sense on several levels, as while the blood elves did not know that they were using demonic energy, they acquired their glowing green eyes just by living in proximity to it - the fel crystals strewn around Quel'Thalas were likely the source of the power mentioned to be upholding the blood elves' structures in place of the Sunwell, which did the same before its destruction. The blood elves, of course, were living around these crystals during this time.
- Similar red crystals called Bloodgem Crystals, primarily used by the blood elves in Outland, are used in similar ways. They can be siphoned by players if they have a . Blood elf mages suggest that the crystals are blue in their natural state, and that crimson was simply a cosmetic choice.