Vicious: When a vicious weapon strikes an opponent, it creates a flash of disruptive energy that resonates between the opponent and the wielder. This energy deals an extra 2d6 points of damage to the opponent and 1d6 points of damage to the wielder. Only melee weapons can be vicious.
If a demon with DR 10/good wields a vicious weapon (considered evil alignment), does that mean this demon can enjoy the 2d6 extra damage without any drawbacks?
First, it is not the damage type of the weapon, because the energy is dealing the damage, not the weapon.
Second, no damage type is given for the energy (such as positive or negative energy). So from a mechanics perspective, it is untyped damage.
This is likely to make any kind of shenanigans hard: the downside of the weapon that is balancing the extra damage is that it also deals damage to the wielder. If that damage was typed, it would be easier to get around it with protection from energy, or by abusing the weapon dealing negative energy as an undead that would be healed by it.
Furthermore, Damage Reduction only applies to “physical” damage, not energy damage like cold or fire, or here an unnamed energy. So, the demon will not have a free ride with it, either.
