Marshadow is a pretty good Pokemon in Anything Goes. It has great STAB moves, high Speed, decent Attack, and Technician.
Marshadow @ Life Orb
Ability: Technician
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Poltergeist
- Close Combat
- Shadow Sneak
- Rock Tomb / Bulk Up
However, it faces competition as a Ghost type from Calyrex-Shadow, the best Pokemon in Anything Goes. Also notice how I said decent Attack. 125 is good and all especially when Shadow Sneak and Rock Tomb are boosted by Technician, however Calyrex-Shadow has much more offensive power unlike Marshadow, its movepool isn't exactly as limited, with things like Psyshock, Draining Kiss, Leaf Storm, Trick, Aromatherapy, Substitute, Nasty Plot, and a more reliable Ghost STAB in Astral Barrage. Caly can run multiple sets i.e. Choice Specs, Choice Scarf, Focus Sash (Defog support from Ho-oh and/or Yveltal is mandatory for Sash sets), Sub+Seed, Nasty Plot 3 attacks... Marshadow is pretty much stuck using its Life Orb set which makes it very predictable. However, Marshadow's access to Shadow Sneak and Calyrex-S's frailty and 4x Ghost weakness means Marshadow is great at removing the most dangerous Pokemon in the game. Of course, Yveltal and Ditto can do that too.