During the BT13 revealing time, nobody would expect that the Belphemon deck would be popular in this meta. It is a very interesting deck, easy to play, fast enough for purple color, strong protection with Belphemon Sleep Mode and OTK with Belphemon Rage Mode.
Main Combo
The deck core combo of course, relying in on the duo BT6 Belphemon Sleep Mode and Rage Mode, but the frame that build and run the whole deck would be *Gizumon* unknown series.
With the support of Eyesmon: Scatter Mode's draw and trash mechanic, these Gizumon somehow can easily be played with the cheapest cost, do one attack in next turn then summon another Gizumon if it is destroyed.
The Lv5 Gizumon: XT is the key card of the deck. We can utilise the effect to destroy Eyesmon Scatter Mode or the LV4 Gizumon: AT; If there is a Akihiro Kurata tamer on the field, we can destroy this LV5 Gizumon: XT to play Belphemon Sleep Mode for just 2cost using Kurata's effect.
Once the sleep mode on board, there is nothing can touch him, except for the "attack opponent's unsuspended Digimon" of LV5 BT8 MetalGreymon (inherited effect).
The Belphemon OTK
The Belphemon Sleep Mode is actually an ultimate protection for the Rage Mode, there is no chance to destroy them if you are not playing BlackWarGreymon or Wargreymon. The Rage Mode, the the next turn when it wakes up, it can easily do 4 checks with 17000DP.
There are 2 different ways to move up to LV6 Belphemon sleep mode, one – to destroy the lv5 Gizumon XT to play the sleep mode for 2 cost as mentioned above. The second one, you can evolve into Astamon in the same turn when Astamon is evolved, the main goal is to let Belphemon stay in the Sleep Mode.
Because there is nothing can touch the sleep mode, so this deck have a very minor disadvantage against deck that bound back to hand like MirageGao (you can't trigger On Deletion effects). The LV5 Astamon and Gizumon XT able to proceed with the strategy in the same turn they are played, not stay till next turn to get it bounce back.
The other problem is we cannot draw the Sleep Mode and have to move on with the vulnerable Rage Mode, lolx, or opponent play the blocker (Royal Knight). The Tamer Kurata's "End of Opponent's turn" effect can only destroy the opponent's LV6 Digimon, it can't do anything with Royal Knight 's Craniamon, while other blockers are not lv6 Digimon (mostly).
But in early of the game, if we are able to draw many Gizumon* in hand then the game will run very fast, we may be able to finish opponent's security before they can set up the defence against this deck.
And if you are reading this article, do check out the other version of Gizumon + Anubismon Rush, there are some tournament winning decks of this combo in BT13 decklist.