Aldanon is a wealthy, yet absent-minded, sage living in the Blacklake district of Neverwinter. Aldanon had come into the possession of one of the silver shards from the Sword of Gith. When the PC arrived in Neverwinter with a shard, the player was eventually able to visit Aldanon in his mansion. The sage was interested in the PC's shard and Duncan's shard, allowing him to compare them to the one he had. After a quick test, he finally determined they were pieces of a Githyanki silver sword.
Source: Wikipedia, "List of Neverwinter Nights characters", available under the CC-BY-SA License.