Clearly Light Is Not Good, necessarily, since blue magic is used as a rule by agents of a government clearly depicted as evil. Although the Shadowdancers use blue magic, we've seen Viviana swear by Bhaal (although this might have been intentionally profane), and now we see a single character use a synthesis of both blue and red magic. Although red magic has so far only been used for evil purposes, the only statement that red magic or Bhaal are inherently evil comes from a ten-year-old in the process of being indoctrinated by expansionist tyrants. As Lilith (itself a demonic name for a good character) says, "I'm going to Bhaal - will you come along?"
Eldor is an elf.
He clipped his ears and is now trying to break in and get revenge on the elves that spurned him, using the Tower and Lilith somehow.
Confirmed: he modified his appearance with permanent spell. Though he isn't spurned by elves, he's working with them to destroy Tower using Lilith.