Shilukar is a dark elf "thief and mage" (per the wanted poster) that has been working in Ptolus.

He is wanted, dead or alive, for the theft of a religious idol of the beast-god Ravvan from a museum in Oldtown. 

You have run into signs of Shilukar at Linech Cran's compound (he began underwriting Linech when he ran afoul of the Balacazars), and you have seen evidence of him searching for something in the Vault of the Serpent Monks.  The dwarf Ruror Redblade told you it was a key. 

While exploring the vault, Shilukar confronted you virtually, using a hologram device, and insulted and threatened you.

You later made an assault on his lair, and although you defeated his entire cadre of minions, Shilukar himself escaped into the city sewer using an invisibility spell.  In his lair you recovered the stolen idol, and found that he was experimenting with chaositech.  The key he was seeking was to open a chaos-formed chest, that cannot be unlocked by means other than a chaos key.

Months later, you learned that Shilukar was now working with the Vladaams, to somehow exploit the Demon-Possessed Watch.