Okay, so players found monsters with a "White Shadow." They are wondering what it means, and I think you should know this as well. Have you noticed your NPC Partners said, "Is this Mutation?" ~Sarisa, "This is gonna get ugly..." ~Kai, "More Mutants..." ~Reve, "What is this? Mutation?" ~Ogi.

So you probably wonder what's so great about White Shadowed Beasts. Well, here's a good thing and bad thing about them:

Good Things
You gain higher EXP than regular ones give
The Drop Item is Boosted (So if you're looking for a certain rare, now's your chance!)
If it's on (Weak) Rare Hostiles, you'll get something good for it (Super Difficulty to be exact)

Bad Things
The Hostile has a Higher HP than regular ones do
The Hostile is a bit stronger than regular ones
If it's on (Strong) Rare Hostiles, you'd be screwed already (if you're on Super Difficulty)

White Shadowed Beasts do not make Rare Hostiles appear after beating or meeting one. And you should notice the white glow under the Hostile. Lets say a Rare Zaphobos has a White Shadow and on Super Difficulty, you'd want the bloody red sword it drops. Once you kill it, there's a good chance you may get it--sometimes you may not. It's just luck (which no one believes...)

Now that you understand these so called "Mutations" you better keep your eye out for them. Your NPC partners will let you know when they see one. Good luck. :D