"The Malice of Mai Cheng 麦城之恨 （"mài chéng zhī hèn")
(Note: The city of Mai Cheng was the location where Guan Yu was ultimately captured and executed)
Why is he a Demon:
It seems redundant to create yet another supernatural version of Guan Yu. Afterall, it would seem that Demi-God Guan Yu is already overkill. Yes, it does seem unnecessary and unjustified, but what the hell!! The more the merrier, right?
Based on the abilities written on the card, there does not seem to be much connection between the phantom of Guan Yu and this character, other than the translated description and the shamelessly ripped-off image.
Still, that does not mean I do not appreciate this character. His abilities can be pretty intense and gives him more killing time than most other characters. Those abilities are powerful enough to warrant him "cheat-character" status... "Demon"!
Character ability 1: "Devil of War 武魔 (wǔ mó)"
In the action phase, whenever an ATTACK 杀 card is used (regardless of effect), you can immediately draw 1 card from the deck.
Character ability 2: "Fall-back 拖刀 (tuō dāo)"
Whenever you successfully evade an ATTACK from any player, you can immediately use an ATTACK on any player within your attacking range.
Ability's relation to story:
Practically none. You get the impression that the abilities were first created before any random excuse for a character was conjured up as a vessel for those abilities. "Fall-back" may seem like it had to do with Guan Yu fighting a retreat strategy before his capture, but that was not quite the case in the story.
Demon Guan Yu has extra killing time thanks to his 2nd ability "Fall-back". This guy does not need the crossbow, but instead can just wait for someone to use ATTACK on him, winning him another chance to strike that is outside his turn. Furthermore, his 1st ability "Devil of War" assures a well-stocked hand as long as he plays aggressively. With him on your team, feel free to bounce your ATTACK off him to reach someone else outside your range. In summary, I feel he is a combination of Da Qiao 大乔 and Lu Xun 陆逊.