Cardinal Crimson Promotion, also known as the True Crimson Dragon Emperor, is the upgraded form of the Scale Mail after Issei successfully convinces the past hosts of the Boosted Gear to follow him and 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.
The Cardinal Crimson Promotion generates a crimson dragon armor that incorporates all three Evil Pieces traits, making it the most balanced and powerful form of Issei's Scale Mail. In this form, he is capable of using enhanced versions of the Illegal Move Triaina, however, this form was unstable and it consumed too much energy, rendering it ineffective for long battles. After awakening it for the first time, Issei was able to fight against Sairaorg Bael in his Regulus Rey Leather Rex who previously overpowered him in his Welsh Dragonic Rook Form. Cardinal Crimson Promotion is his answer to a power different from the Juggernaut Drive after successfully overcoming the curse of the Juggernaut Drive.
It is later revealed in Volume 11, that in order to both stabilize and strengthen his Crimson Cardinal Promotion, he would first need to master the individual Illegal Move Triaina forms. Issei used this form against the legendary Evil Dragon, Grendel, which allowed him to fight the resurrected dragon on equal terms, with the latter praised him for his power as most opponents aren't powerful enough to fight him head-on. Later on, in Volume 17, with the help of his Dividing Wyvern Faries, Issei was able to defeat Euclid Lucifuge, who possessed the replica Boosted Gear combined with his Satan-Class power and overwhelmed Issei in their previous encounter.
In Volume 22, it is revealed that Issei can enter True Queen without having to chant, and due to Diabolos Dragon God, it's power has been increased, with the form no longer being as stamina intense as before. During the Rating Game against Team Lightning, Issei managed to overwhelm Baraqiel, with the Cadre stating he cannot defeat Issei in contest of strength. In True Volume 1, Ddraig reveals that Issei can fight Satan-class Devils or equally strong beings in this form.
- Star Sonic Booster (スター・ソニック・ブースター, Sutā Sonikku Būsutā): Used while in Cardinal Crimson Promotion. Grants the user godlike speed that far surpasses Welsh Sonic Boost Knight's.
- Solid Impact Booster (ソリッド・インパクト・ブースター, Soriddo Inpakuto Būsutā): 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. Issei can also enhance his Solid Impact Booster with Ascalon's dragon-slaying power to strengthen his blows against Dragon opponents.
- Fang Blast Booster (ファング・ブラスト・ブースター, Fangu Burasuto Būsutā): 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 (白龍皇の妖精達, Dibaidingu Waibān Fearī): 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 to Rias to create her own variation of the Boosted Gear Scale Mail armor called Crimson Extinction Dragonar. In Volume 23, Issei revealed that he is capable of attaching the red Wyverns to Xenovia to create a variation of the Boosted Gear Scale Mail armor called Crimson Destruction Dragonar.
Longinus Smasher (ロンギヌス・スマッシャー, Ronginusu Sumasshā): In Volume 17, Issei gains access to this ability when the Red Wyverns used Boost on him while in this form. An ability was initially available only to the Juggernaut Drive that causes a launcher to appear on the armor's chest and fire a powerfully destructive beam. This leaves 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.
Tail Blade (テールブレード, Tēru Burēdo): Using the Ascalon II Prototype, Issei with his tail of his armor can attack with its blade and lengthened the tail towards his enemies at high speed.
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!
- 汝らに誓おう 真紅の光輝く未来を見せると
- Ware, mezameru wa
- Ha no ri o sutesarishi, Sekiryūtei nari
- Mugen no kibō to yume o mune ni kakae, ōdō o iku
- Ware, Akaki Ryū no Ōja to narite
- Nanji-ra ni chikaou shinku no hikari kagayaku mirai o miseru to
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 is a deep scarlet color so the armor is actually a mixture of deep scarlet and crimson red.
- Cardinal Crimson Promotion can be considered Issei's Ex Side Balance Breaker.
- Unlocking Cardinal Crimson Promotion transformed one of Issei's Evil Pieces into a Mutation Piece, making it the fourth Mutation Pieces inside him in addition to the 3 Mutation Pieces that were transformed after he attained Illegal Move Triaina. After Issei attained Diabolos Dragon, the remaining four pieces were transformed into Mutation Pieces.
- Cardinal Crimson Promotion is is Issei's answer to a form different from Juggernaut Drive, which can be considered as Issei's counterpart to Vali's Empireo Juggernaut Overdrive.
- 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.