Cardinal Crimson Promotion, also known as the True Crimson Dragon Emperor, is the upgraded form of the Scale Mail after Issei successfully unlocks the "True Queen" form.
In Volume 8 of the light novels, one of the Four Great Satans, Ajuka Beelzebub, creator of the Evil Pieces system, remodels Issei's Pawn Evil Pieces after he learned that the original program written by him was overwritten by a different code, which he speculates to be the effects of the Juggernaut Drive, remodeling it to adapt to the power of the Red Dragon Emperor.
Debuting in Volume 10 of the light novels during Rias' Rating Game battle against Sairaorg Bael, Issei manages to change the view of the past possessors of the Boosted Gear along with Rias' help, allows Issei to access the Queen mode and unlock the Cardinal Crimson mode. In this form the color of the Scale Mail armor changes from red to crimson, and was given the name Cardinal Crimson Queen by Sairaorg.
In Volume 11, Issei renames the form into the Cardinal Crimson Promotion and creates a different chant for accessing this form.
In Volume 22, it is revealed that Issei can enter True Queen without having to chant, and due to Diabolos Dragon God mode, its power has been increased.
Cardinal Crimson Promotion incorporates all three Evil Pieces traits, making it the most balanced and most powerful form of Issei's Scale Mail. The Cardinal Crimson Promotion is Issei's answer to a power different from the Juggernaut Drive after successfully overcoming the curse of the Juggernaut Drive. However, this form is still unstable and consumes too much energy, rendering it ineffective for long battles. This form also requires mastering the three forms of Illegal Move Trident in order to stabilize its powers.
- Star Sonic Booster: Used while in Cardinal Crimson Promotion. Grants the user godlike speed that far surpasses Welsh Sonic Boost Knight's.
- Solid Impact Booster: Used while in Cardinal Crimson Promotion. Morphs one of Cardinal Crimson Promotion's fists into one of the Welsh Dragonic Rook's, allowing for an enhanced version of Solid Impact.
- Fang Blast Booster: Used while in Cardinal Crimson Promotion. Two cannons hidden in the wings are utilized to fire a powerful beam attack.
- Crimson Blaster (クリムゾンブラスター Kurimuzon Burasutā): An enhanced version of Welsh Blaster Bishop's "Dragon Blaster". Issei can concentrate its attack to one point when targeting a single target. In Volume 16, Issei could use this technique in tandem with Ascalon's dragon-slaying power, rendering it capable of injuring even Crom Cruach, the strongest Evil Dragon.
Dividing Wyvern Fairy: An ability that allows Issei to create small Wyverns from the gems of his armor that are able to use the basic abilities of the two Heavenly Dragons by changing their color between red and white, the Wyverns however requires Issei's stamina to stay active. In Volume 16, Issei summons the white Wyverns for the first time when they used Albion's ability that he took in Volume 4 to use Divide and to Reflect incoming attacks. In Volume 17, Issei manages to change the Wyverns into red at will where they are able to use Ddraig's powers of Boost, Transfer and Penetrate instead. After training with Rias, Issei manages to make use of the red Wyverns to attach themselves on Rias to create her own variation of the Boosted Gear Scale Mail armor called Crimson Extinct Dragonar.
Longinus Smasher: In Volume 17, Issei gains access to this ability when the Red Wyverns used Boost on him while in this form. An ability initially available only to the Juggernaut Drive that causes a launcher to appear on the armor's chest and fire a powerful destructive beam. This leaves a strong fatigue on Issei and depending on how one uses it, it can change the environment. Due to its immense power, this ability has a very long recharge period, lasting at least a month.
When Issei first used Cardinal Crimson Promotion, he uses a modified version of the chant for Juggernaut Drive.
- I, who is about to awaken
- Am the Red Dragon Emperor who has discarded the principles of domination
- I shall walk the road of righteousness by having infinite hopes and dreams
- I shall become the King of Crimson Dragon
- And I promise you all! I shall show you the future which shines in true crimson light!
Issei uses a different chant with some old wordings in Volume 11 during his battle with Shalba Beelzebub.
- I, who is about to awaken
- Am the Red Dragon Emperor who holds the truth of the king up high
- Holding the infinite hopes and unbreakable dreams and walking the path of righteousness
- I will become an Emperor of Crimson Dragon
- And I will lead you to the Path of Heaven, glowing in deep crimson light!
- Ware, mezameru wa
- Ō no shinri o ten ni kakageshi Sekiryūtei nari
- Mugen no kibō to fumetsu no yume o daite ōdō o iku
- Ware, akaki ryū no teiō to narite
- Nanji o shinku ni hikarikagayaku tendō e michibikou
After which the Boosted Gear announces "Cardinal Crimson Full Drive!"
- Cardinal Crimson Promotion is modeled after the ZGMF-X10A Freedom Gundam from Mobile Suit Gundam SEED.
- Its dragon wings bears a striking resemblance to Gunren S.E.I.T.E.N. Eight Elements's energy wings from Code Geass.
- Cardinal is a deep scarlet color so the armor is actually a mixture of deep scarlet and crimson red.