Demonic Spellcasting. The Demon Warrior's spellcasting ability is Wisdom (spell save DC 12, +5 to hit with spell attacks.
Multiattack. The Demon Warrior makes three flaming blade attacks
Flaming blade. Mellee weapon attack +7 to hit, reach 5ft., one target. Hit: 13 (2d6 + 6) plus the target must make a DC 10 dexterity saving throw or take 20 (4d10) fire damage. This is a magical weapon, and the Demon Warrior can extinguish and light the blade at will whilst it is holding the blade. If the blade is lit then it does not do fire damage.
They can be used in any enviroment where an Abyssal Portal is present, or where a Demonic incursion has traveled to. If left to there own devices, they will gravitate towards places of fire such as volcanoes, or dark places like cemeteries and other places of death.