At xWhyNotx, yeah I get what you mean on it having been endorsed... and I even mentioned that in my previous post. It all really depends on how you use it I guess. If it becomes an important part of events or series of events I guess it can work. To be honest, I barely consider Shadow Lugia a real Pokemon because of the fact that it just is an evil version of the angel-feather-colored Lugia we know and love.
But yeah, Pokemon XD is a GameCube game that popularized Shadow (or the more popularly known "Dark") Pokemon. The criminal organization stole Pokemon, manipulated their feelings and emotions, and made Pokemon evil. There were even Special movesets that the Shadow pokemon knew in place of their normal movesets. The attacks were stronger, but often involved a recoil of some sort (but not always). Their goal was to make the perfect Shadow Pokemon that couldn't be turned back to normal. They were almost successful with XD001 (Shadow Lugia). But the main character used a Snag Machine to capture the Shadow Pokemon and by (here is where it gets sappy) loving the Shadow Pokemon, you revert the Pokemon back to their normal form. XD001 is the hardest to revert involving a tedious and annoying process I won't get into, but you can Google. It's a good game that I suggest you try.
If you need a mapper, I can help ya.