The creature you saw in the opening wasn't implemented in the game even though it was supposed to. Since it was shown in the cutscene it's quite expected to encounter it in game.
The creature on the ground is actually a "normal" enemy and since he stands out from the others I guess that's why it leads some people to believe it was maybe the creature from the intro.
The tutorial was placed very quickly at the last minute and I didn't expect the text to be affected by light so that's why there is this strange behavior but it shouldn't be hard to fix I'm sure!
Didn't play that one!