Mythic Rulers have an almost auto win against shaddoll, the problem is their consistency. I've been working with squids to create a consistent mythic ruler build.
Monsters: 18
2x Blue-Eyes White Dragon
1x Flamvell Guard
1x Blaster, Dragon Ruler of Infernos
1x Debris Dragon
1x Eclipse Wyvern
2x Koa'ki Meiru Drago
2x Mathematician
2x Card Trooper
1x Mythic Water Dragon
1x Red-Eyes Darkness Metal Dragon
1x Redox, Dragon Ruler of Boulders
1x The White Stone of Legend
1x Tempest, Dragon Ruler of Storms
1x Tidal, Dragon Ruler of Waterfalls
Spells: 15
1x Burial from a Different Dimension
3x Dragon Shrine
1x Foolish Burial
1x Gold Sarcophagus
3x Pot of Duality
3x Soul Charge
3x Trade-In
Traps:7
2x Phoenix Wingblast
2x Trap Stun
3x Vanity's Emptiness
Extra Deck: 15
1x Azure-Eyes Silver Dragon
1x Black Rose Dragon
1x Colossal Fighter
1x Crimson Blader
1x Scrap Dragon
1x Star Eater
1x Stardust Dragon
1x Stardust Spark Dragon
1x Alsei,the Sylvan High Protector
1x Castel, the Sky Blaster Musketeer
1x Divine Dragon Knight Felgrand
1x Hieratic Sun Overlord Dragon of Heliopolis
2x Mecha Phantom Beast Dracossack
1x Number 11: Big Eye
Some other good picks are Thought Ruler Archfiend and Hot Red Dragon Archfiend (basically the same effect as heliopolis but easier to make. Heliopolis can hit spells, traps, and monsters.)
https://i.imgur.com/ipQ7y0s.pngSince some of the choices are unorthodox I'll explain them.
1. Wyvern allows you to search red eyes which allows you to otk so easily.
2. Drago single handedly beats Burning Abyss, Tellas, and Shaddolls. Its searchable by tempest.
3. Water, but no tree. Tree was another normal summon, whpich makes it too much. Water is used mainly for the summon of red eyes and rank 8 plays with scrap.
4. Math is basically more copies of blue eyes and dragon shrine. It allows you to search blueyes (making you're trade ins live), and red eyes. It's also an earth for redox and water.
5. Red-Eyes allows for crazy otks. its also a monster reborn with no cost.
6. Duality = Consistency
7. Trap stun. The main purpose of this strategy is too grind and when you have enough resources to push for game flip trap stun to otk.