This unit actually reminds me a lot of The Demon World Marquis, Amon, primarily because of the Dark Lord's Limit Break, but there are several subtle differences that completely change the way they are played. I personally prefer Amon, but let's take a look into The Dark Lord, and see how he holds up.
His Limit Break Skill is All there is to resemble him to Amon, but it could, possibly be more threatening. When you Counterblast 2 for his skill, and Soulcharge 2 cards, and he gains 1k for every Dark Irregular Unit in your Soul, until the end of your turn. It is very important to note that it is an "Act" Skill, meaning two very important things.
Firstly, any additions to the Soul after his skill is used will not be applied to his boost. Part of the cost of this skill is a Soulcharge 2, so that is already in the soul before the boost is applied, and therefore is added to the total.
Secondly, because this is a limit break skill, you have 4 or more damage, and are able to use his skill a second time in the same turn. The Skill is stack-able and static, so you can use it the first time, and get your boost, and then use it a second time to get that same boost +2k because of the second Soulcharge 2.
His other skill penalizes you for having any units that are not Dark Irregulars, by giving himself a -2k to his Power
Strategies and game play:
Dark Lord of the Abyss is likely to be used in a similar fashion as Demon World Marquis, Amon, delivering devastating power to the opponent's Vanguard that becomes very difficult to stop unless a Perfect guard is used. With a natural 11k power, his usual minimum is 18k without boosts when his skill is used once; twice is about 27k before boosting. He is designed for 2~3 hard hits, or 1 very hard hit that your opponent must always beware of.
Now, Amon's skill has a cost of 1 counterblast, and putting one Rearguard unit into the soul, while Dark Lord is a Counterblast 2 and a Soul Charge 2; both would provide equal boosting when matched up. The differences between Amon, and Dark Lord is that the Dark Lord can surpass Amon very quickly in power, due to his ability to stack the boost from his skills. Any height Amon can reach, Dark Lord can hit almost twice over.
Amon's Boost skill, contrary to what was conceived upon reading this, does not have a cost, and is actually a "Cont" skill, meaning, during your turn, he will be at his boosted Power with no cost, while Dark Lord needs to pay to play. Now, I mentioned that little ditty about Amon's skill having a cost, that was to retire one of your opponent's units. So at a similar cost to each, one gets massive, almost unstoppable power, while the other gets a smaller boost, but rids you opponent of a rearguard in the process. Really just a matter of preference.
Combos with other cards:
-Decadent Succubus: As the Grade 2 Vanguard before Dark Lord, one is able to do massive Soulcharging at little cost. You are able to empty out your hand, to Soulcharge to an upwards of 5 times (Triggers not included) and then the two (Minimum) that should be in your soul upon Decadent's ride, Dark Lord is looking at a +10k boost when his skill is activated, plus another 12k if used twice (That's 33k before the boost from attacking, and a full Rearguard, ready to lay the smack down.)
-Vermilion Gatekeeper: Soulcharge as soon as you first ride.
-Alluring Succubus: Soulcharge upon Ride/Call.
-Blue Dust: Soulcharge upon Hit. Gives your opponent something to waste guards on, because of the ever dreaded Soulcharge dependent on the opponent's actions.
Ways to counteract it:
-Perfect guard: Let's be honest, it's a very large attack when it goes all out, are you really going to spend all those cards trying to guard a 47k Attack? Even before boosting? yeah, I didn't think so.
-Be patient: His skill is a Limit Break, so they need four damage to do anything with it. Keep them waiting at three until you can knock out three damage at once.
-Be crazy aggressive: In direct opposition the the prior strategy, it is possible to go through enough damage, that your opponent can't even get the cards to guard with, let alone ride into something that fierce.
-11k base Power makes guarding a little easier
-Breaches 25k consistently
-Skill can only be used twice if no healing occurs
-Penalty for a mixed Rearguard
-Only good skill is Vanguard only
-Skill is not continuous
Comes in RRR and SP in the Rampage of The Beast King.
Artwork and aesthetics:
I personally don't care much for it. Not to say it is bad, nor to say it does not fit with the art of the other Dark Irregulars, but this one doesn't quite work for me. He is stepping out of, what i assume is, a portal of light, with dark armor, and red bolts of electricity coming from him, or the portal. His armor sort of reminds me of Werewolf Seiger, not surprising by the way. He should be very intimidating, but he's just walking out of the light like he's in a bad mood.
7 out of 10
I've been alternating Dark Lord and Amon for quite some time now, and I really can't tell you which is better. Amon is able to make full use of the Damage Zone with his skill, while Dark Lord has a waste of 1 unflipped damage. Dark Lord is an ungodly beast, while Amon is the next runner up. Amon Retires the Rearguard while pumping himself up; Dark Lord... doesn't. Dark Lord is just a fancy way of saying, "My attack is hitting if you don't have a Perfect Guard," While Amon does damage, boost himself, and gets rid of your opponent's Rearguard. As I said earlier, it is really just a matter of preference.