Embershade wasn't an element of harmony, nor was she really anything beyond a normal Pegasus Pony. The only thing that made her special was that she was totally, inescapably, alone. When Discord offered her friendship, she could see no happy option but to agree.
After his defeat, Embershade struggles to fit in to the world she nearly cast into never ending chaos.
-edit- There's no sex or gore as of yet, however it is expected.