Crystron R.B.

Essentially, you're adding Machine of the Closed Heaven (Booster) so you can make Machinesmith's Desirae (Booster pointing at an arm w/ Funk Dock) as either an additional endboard piece, or as a backup plan if you get handtrapped too much. Best case, you can end on Infinity + Tristaros + Cluster + Dragster + Booster/Dock/Arm, but that's a ~3 card combo. It's also not awful to open RB, fire a Rocket as a boardbreaker/interaction bait, and then still get full Crystron after (eg: Special Limb > Normal Smiger > Link Booster add Dock > Dock add Rocket > Rocket inherent summon > Rocket effect > Dock summon > Banish Smiger to add Inclusion > Play normally).

The basic endboard combo to add RB requires summoning Prasiortle somehow, and having any Crystron monster in hand (added by Eleskeletus, Thystvern):

Summon Prasiortle > link Clockwork Knight > Prasiortle summon from hand > Link 2 Booster w/ Clockwork + Crystron > add Dock > Dock, add Driller/Cutter > Booster effect, summon from hand.

EDIT July 2025: Oh, Scrap Recycler fixes a lot of the consistency issues, while still freeing up a non-engine slot. Apart from being a backup 1-card starter for Crystron, with any RB maindeck monster in hand:

Inherent summon RB > Normal Scrap Recycler, eff foolish Crystron (Smiger, usually) > Link SS to Clockwork Knight > CK eff, target RB, resummon Scrap Recycler, foolish another Crystron (Thyst/Fefnir) > Link 2 Booster, add Funk Dock > Funk Dock add RB > Play Crystron normally off the two foolishes >> Booster eff to summon from grave or hand.

That opener can do full Crystron combo through 1 interruption, and should still get a Booster through 2.

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Unfortunately, they haven't printed Machinesmith's Requiem yet, so none of the RB parts are starters on their own, but Driller and Rocket are viable for 2-card combos into full Crystron, whereas Cutter can only 2-card into Booster/Brute unless you run Hi-Speedroid Kendama or something (Powered Inzektron doesn't work, Tristaros can't pop it).

R.B. Stage Landing is 0-1 in this deck because the lock makes it a brick in most hands, but it's still worth considering as a 1-of because on its own it's a 1-card RB combo, and also turns Dock into a 1-card combo. Note that you'd also need to add Brute Blues to the Extra, but also Brute Blues isn't worth playing without Stage Landing since it's a lot of material for the same amount of interruptions as Booster.

Added Accel Synchron + Return Zero for those times when you get both Machine Synchro and RB locked, but honestly those are flex slots.