Forum:A question on Vhaerauns weapons

I've noticed the drow god Vhaeraun has been cited to carry 2 weapons, usually Night Shadow and Shadowflash. However, I recently read one of Lisa Smedmans novels, Sacrifice of the Widow, and right before he entered Eilistraee's realm and died, he was noted as carrying Night Shadow and Silverflash. I am curious to know how this came about from Shadowflash to Silverflash? I Appreciate any info.