Yello, Advisor of Dark World seems actually not to overpowered, as he only enables your DW monster's bonus effects, but regarding the fact, that those can be pretty damn crazy (I'm lookin at you Sillva), I'm unsure if it would produce healthy gameplay
His Spell/Trap lineup is I think just three Sanctuary in the Sky and a bunch of Counter Traps
Starting with Gen VIs Pokmon X and Y on the 3DS, the odds of encountering Shiny Pokmon doubled to 1 in 4,096, or 0.024%
Those that have mastered the basics of regular duels will find Turbo duels to feel like a natural progression for the game
Despite being a low-level card, costing only two ink to play and having low stats overall, the non-Enchanted form is still a Legendary card