Darkness Pokemon often have some powerful abilities that can interact with Pokemon on the bench as well as active Pokemon
The Dark Illusion gives Spellcasters access to powerful cards like Magician Navigation, which Summons a Dark Magician from the hand and another DARK Spellcaster of your choice right from the Deck, then goes on to negate an enemys Spell or Trap
Sultai Arisen The ability to pull cards from your graveyard is inherently powerful and both commanders, Kotis, Sibsig Champion and Teval, the Balanced Scale let you do that every turn
I have a sacrifice deck helmed by Tevesh Szat, Doom of Fools partnered with Rograkh, Son of Rohgahh thats fun, and a Rohgahh, Kher Keep Overlord deck thats split between Kobolds and Dragons that I think is a hoot
The goblins are in charge of maintenance
It's possible to use him to shoot down creature decks, or players can use his Hadoken to be more aggressive by effectively doubling his damage each turn