Search Eternal Soul, a dragon-type monster (or Xyz Summon one from the Extra Deck), Dark Magician or King of the Swamp (as substitute) and Polymerization. When you collected all pieces, you are ready to go. You can also use The Eye of Timaeus to do so, but you have to Special Summon Dark Magician (or Magician of Dark Illusion) first. Also, The Eye of Timaeus cannot be searched unlike Polymerization.
Nothing can stop Dark Magician the Dragon Knight + Eternal Soul. Save Eternal Soul's effect to revive your fusion monsters from the GY in case they get kaijued or anything.