Greevil uses a team of six shadow Pokemon, plus XD001. He uses the three legendary birds, as well as Rhydon, Tauros, and Exeggutor. I always thought the non-legendaries on this guy's team were kind of random, but then I looked at the tiers for Red and Blue; those three are OU tier from Red and Blue, and Greevil's old. This was a shout out to the Gen Wunners.
When you try to retrieve your Snag Machine from Gonzap before heading to the Cipher Key Lair, he offers to return it to you without a battle if you join their fight against Cipher, saying that they plan to snag Cipher's Shadow Pokemon. He was probably lying about this, because they wouldn't have known which Pokemon to take (unless they used a Shadow move) because they didn't take the Aura Reader, which, aside from having Rui with you, is the only reliable method for normal people to determine whether or not they're battling a Shadow Pokemon.
There are some very deep symbolic meanings behind the concept of Shadow Pokemon and Shadow Lugia.
Being clean is the soul of Shinto religion. Therefore, the act of creating shadow Pokemon is one of the most heinous and inexcusable crimes in the franchise while purifying them is one of the most noble and heroic deeds.
Silver symbolizes the moon which has both a light side (full moon) and a dark side (new moon) with Shadow Lugia as the dark side.
"Lunaticus" is a term that was used to describe a type of insanity that was supposedly induced by exposure to moonlight. Shadow Lugia symbolizes lunacy or a creation made with delusions of power, wealth, and supremacy.
A Silver medal has become synonymous with downfall stories where a competitor, either a young aspirant that's just starting off or a seasoned veteran, puts on a very good performance but just narrowly misses getting the gold medal. The psychological backlash of coming so close and failing to become number 1 can erode a person's self-esteem so badly that they can never perform to their fullest again, leading to a depressing career of mediocrity and even early retirement. Because to them, missing the Gold Medal is a Fate Worse than Death. A Lugia falling afoul of Cipher, despite being among the most powerful legendaries, and being turned into a Shadow Lugia is truly a terrible tragedy in itself.
Gold will retain its luster and purity over the years because it's stable and doesn't tarnish. On the other hand, Silver requires constant care to remain pristine.
Now that one thinks about it, Orre is a Nightmare Fuel Refinery, and Fridge Horror is merely a byproduct. A desert region with almost no wild Pokémon, criminal presence out the ass, a horrifically ineffectual police departmenteven by Pokémon standards, and Cipher, who MindRapes Pokémon for power and profit, trains their personnel in the arts of spreading terror, and has no qualms whatsoever about hurting - or even killing - anyone who obstructs their dominion (see the note above about the missing sailors - that's Cipher's handiwork). Researching every brand of Fridge Horror in-depth is such an arduous process that I will instead redirect you to Pokémon's Nightmare Fuel page so you can research the Orre folder for yourself. But what's scarier about all this? How many games outside of Colosseum and XD reference Orre by name? Fucking zero - not even Black and White utter a word of this. Then again, what's listed above may have something to do with the lack of references... sweet dreams.
Greevil wanting to have Shadow Pokemon that don't need underlings to control them sounds worse with the fact that the S.S. Libra caper at the beginning was able to be done merely by remote commands by a mook to Shadow Lugia. If the Shadow Pokémon process was perfected Greevil could have very well have done it with any number of Shadow Pokémon and coordinated practically whatever he wanted including attacking people. And that's without the extremely powerful legendary.