APPROACH WITH CAUTION!
For those of you who don't know about Nightmare from my Deer Online Status
Page or his
Bio In general. Let me explain what's going on in the best of ways possible.
Nightmare only allows 2 people to get close to him (3 if you include Leea) and those two are Laurette and Sithrim. Sithrim because he feels safe around the stag for protecting him against the 'holy' things that can plague him, and Laurette because he feels a need to help protect her. With recent happening, and with what Beliar did to Laurette he has gone into a semi-deadly "Beautiful Nightmare" State (See Bio for details)
Why is this so dangerous? Nightmare... is normally not an aggressive creature when around other deers. In fact, he can tolerate most so long as they do not pester him BEYOND belief. He is only aggressive (While in his Sweet Dream state) when a 'target' is around and even then, he is only aggressive around his target.
Right now however, Nightmare is currently FURIOUS! See
This for details. And it's more so best NOT to approach him while he will be in this state. If he comes around you're deer. I don't expect anyone to run, and really he WILL keep a good distance from those but crazy dorks who approach him will be greeted with an Anger Emote, Roars and rearing/pawing the ground. This is him telling you to GET the heck away.