Necrosaro was a great villian, as Drago said, his motivation went a good bit more than simply "Grr, evil. Smash kill." He was in love with an elf girl who cried ruby tear drops, because of this people were cruel to her to make her cry. Saro became a dark elf and started to strike back at humans.
A neat aspect of the game was that you really got to see a bit of Saro's progression to Necrosaro, you got to meet with the elf girl who's worried about what's happening to him, her home village the people of which looked up to Saro as a hero, not to mention the girl's eventual murder which drives Saro over the edge. Towards the very end you also find out that this was a plot of the demon race, which has been using Saro as much as he's been trying to use them.
For the days of the NES, he was a great villian, a shame what Ryoga's done to him.
I also have some DQ artwork with a nice bit of Saro, can't remember where I downloaded it from. He is indeed most Bishy.