Sepulchral Wyrm
Sepulchral Wyrm is a Demon found in The Obsidian Halls under Wusao Mountain. They appear only in pairs alongside the groups of Magma Sprites.
Sepulchral Wyrms have a lot of health and use two types of attack, basic melee and a fire breath that deals almost no direct fire damage but instead an extreme amount of Burning damage and will easily kill a hero with low Fire Resistance. They rarely use their melee attack, preferring to almost constantly spam their fire breath. This fire breath can be dodged, but even during breath Wyrm will try to hit hero with breath.
Recommended resistances: Fire.
N.B. A hero likely will die if he tries to fight them with low Fire Resistance. It is recommended to get at least 70% resistance, especially considering the fact that usually hero fights them in pairs.
They can drop the valuable Demon's Blood charm.
N.B. As of February 5th of 2022, Sepulchral Wyrms for some reason drop Primal Magma instead of Demon's Blood. This strange behavior was noticed in the latest version of the game vTQ Anniversary v2.10.19714 dated back to January 20th 2022, but it might also occur in earlier versions. This is true even if the game has no DLCs installed. This is likely a bug or an oversight by new developers of the game, because Primal Magma was only introduced in Ragnarök DLC and shouldn't appear in earlier acts.