This is a fairly consistent OTK deck. Be advised this deck has only 1 play if made to go first but you should NEVER GO FIRST. Only go second. If you go first summon 2 of your math mechs and go into link devotee and link disciple. Make I:P and pass, using her to make unicorn on your opponent's turn.
Going Second your basic combo is to use Nabla to special summon Multiply. Then use any of your 3 free summons (Additions, Subtraction, or Sigma) and use Multiply effect on itself or Sigma. Remember Nabla and Sigma are your tuners so you need one of them and Multiply. Now synchro into Final Sigma, triggering Multiply's effect in the GY. Target Final Sigma to make it 6k and go attack. Your opponent can activate any trap or monster effect, but it won't matter because Final Sigma is unaffected. You should be able to deal over 8k damage this way. This deck uses Nibiru & Kaijus to get rid of big boards and pesky monsters like bagooska or apollousa.
A word of caution, this deck is VERY weak to Called by the Grave. This is why we run Ghost Belle & Haunted Mansion. Ghost belle will negate Called by so Sigma can special itself, Division can resolve, and Multiply can make you win. You should be able to make the Final Sigma OTK by summon 4 or 5 so you're safe from Nibiru. Be cognizant of your normal summon; you should only be normal summoning Nabla and Multiply but try to keep either Nabla or Sigma since they're your only Tuners.
210
210
720
420
