I was a bit surprised when I saw X-antibody Dorumon winning a lot in Japan even though we tend to think that black cannot be faster than red/blue/green hybrid. For now, for black X-antibody, we have access only to Dorumon's evolution line, BT6's Alphamon, and Omni X-antibody from BT5 (a white Digimon that can digivolve from either red or blue or a Digimon with [Omnimon] in its name).
This deck's playing style may sound very straightforward, but it's not. There are multiple facets in this deck's gameplay, moving diligently between memory control, draw power, OTK damage, and defense.

This is a basic build for X-antibody Dorumon line that I was playing with. I am still learning more tactics as I practise with this deck, and that has made me recognise the potential of this deck. (You can check for more Dorumon deck profiles in our site).
I chose to run with 6 LV6 Digimons because I feel that my hand will brick if I run any more than that. For LV5 Digimons, besides the 4 copies of DoruGreymon, I feel that it is important to use Warumonzaemon (either 3 or 4 copies) since it is the cheapest cost to play and digivolve among black LV5s.
For LV4 Digimons, 2 copies of blocker Mekanori will give just enough board control against rookies, and forces your opponent to build a proper digivolution line instead of rushing with rookies. This deck needs to stall the game a little in order to perform some of the deck's key strategies, so some LV4 blockers can be useful for this purpose. I also run 2 Tankmons because it is the best vanilla lv4 Digimon costing only 1 to evo and has a respectable 6000 DP, and 1 copy of hybrid Grumblemon as a backup plan for endgame.
For my LV3 Digimons, besides 4 copies of Dorumon the other 3 are very important for the deck. Chuumon is vital when dealing with all the memory cheats in current meta, the promo Sunarizamon is a must-have element that works really well with the X-antibody line and 2 copies of stater set ToyAgumon for that additional draw-power.
The Kouta tamer plays an important role for me to secure the 3 memory at the beginning of turns, while also providing a search for X-antibody Digimon when he is played. The duo tamer meanwhile gives +2 memory when the opponent has 2 or more Digimon in play which is very easy to achieve.
How Do I play this deck
In early game, there is no hurry to attack the opponent's security. I will perform my digivolutions inside the nursing area if it is not safe to move out, otherwise I will move it out and digivolve into LV5 DoruGreymon (and by placing 1 X-antibody card under its digivolution source) to gain a turn invulnerability towards deletion effects and DP-reduction. If possible, I would play Kouta early or a delay option card to maintain a good hand for digivolutions.
While building my digivolution inside the nursing area, I will play a LV5 Warumonzaemon from hand for 5 cost if I need to pass the turn to the opponent.


OTK
With a starting memory of 3 (from Kouta or the duo tamer), I will move Dorugreymon from nursery and digivolve into Dorugoramon for 3-4 security checks (by inheriting Sunarizamon and/or putting another Dorugreymon in his digivolution sources). In addition, his DP can be easily buff past 15000 DP or more when properly built, making him quite a viable OTK machine.
Under more ideal circumstances where I have 5 memory or more, it is possible to digivolve from LV4 to a Dorugreymon and then to Dorugoramon in the same turn, as long as I am inheriting Dorumon or if I can put Dorumon into my digivolution sources along the way. When digivolved this way, Dorugoramon would be able to gain Dorugreymon's turn invulnerability for security checks, somewhat rivalling a red deck's "option jamming"(though this does not protect against non-deletion option effects).

Board Control
An attacking Dorugoramon can easily remove (up to 2 of) your opponent's LV3 and/or LV4 Digimons on the field, since a properly digivolved Dorugoramon will have 6 sources when attacking hence be able to remove 2 6-cost or lower Digimons.
This level of board control is very desirable in this meta, allowing pesky Bokomons to be removed with ease, or erase a wide board of LV4 hybrids or Eyesmons. If left alone, Dorugoramon can begin to delete 7-cost Digimons in the next turn, moving well into the realm of LV5 Digimons.
Depending on matchup and situation, it is also possible to digivolve into Zwart Defeat just to remove an opponent's tamer card that can threaten my game during the next turn.


Defensive Manoeuvres
I play Power Of Breath and Final Zubagon Punch to give this deck a defensive angle.
Power Of Breath will allow me to give Dorugoramon [Reboot] and some immunity, increasing his odds of surviving through the opponent's turn. In addition, when triggered through security this card can pretty much save my game.
Final Zubagon Punch is another card that work wonders with Dorugoramon, granting him a plethora of effects allowing him to hit hard, and block during the opponent's turn. I usually play this card on my Dorugoramon to pass the turn if I do not have enough memory to play it before it attacks.
Another much-overlooked defensive card is Alphamon himself, as when triggered from security will grant a turn protection while adding himself to my hand.
Other smaller additions include a single copy of Shademon (offering a from-security blocker potential) and the fact that we have 4 copies of LV4 blockers in Dorugamon and 2 Mekanoris.
Draw Power
I find that Metal Cannon can be invaluable for a much needed draw power. With a tall stack of Dorugoramon, playing a 2-cost Metal Cannon for a 6-card draw is immense! This can be a great card for turn passing, filling up your hand with solutions for the next turn.
Also, Dorimon and Toyagumon's inheritable effects provide a gradual but consistent drawing power, which helps to manage my hand size as I continue to slot Digimons under digivolution sources.


Final Thoughts
I find this deck being very versatile: to be able to hit as hard as a red deck, and then moving immediately into a defensive mode, can be very painful to the opponent. The game can be pretty much over if they are unable to remove a tall stack Dorugoramon immediately, and the stunners from security can really tilt my opponent's game plan.
Thanks to Rock Braud for pointing out a mistake in my earlier writing, I went back to the drawing board and revised this article after playing another good few rounds (against 3 different decks) to walk through some of the technicalities of this deck.
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LV6 Dorugoramon is a [When Attacking] [Once Per Turn] Affect not a [When Digivolving] effect.
Hi Rock Braud, yes you are right. I made a mistake when conceptualising Dorugoramon's effect in the article (despite playing it correctly a few days before) which shows my unfamiliarity with this deck. I went back to "deck practice mode" after your point out, and has revised this article. Thanks again for pointing me the right direction 🙂