The wise fool?
With regards to Special Energy and what it may or may not do, the big issue is one of balance followed by theme. The short version is that there are plenty of things you can have an Energy do, but keeping it from being overpowered-but-relevant while also being on theme is tricky. A hypothetical new Special Energy version of Darkness Energy could perhaps allow the attacker to ignore all effects on the Defending Pokémon? Discard itself and an Energy from the opponent's Active when something with it attacks? Inflict Sleep?