Unmasking the Enemy

That the message is a trap is beyond dispute, but there is very little choice. The master of assassins has made it quite clear he is not done with you, and failure to accept his invitation could result in the ruin of the Shining Guard. Wherever you go, so will he; nor will he hesitate to bring everything down upon you when the moment is right. It would be wiser to end this charade now.

Fight your way through the Dark Elf army camp to where the message said the Masked Shade would be waiting. Kill the Masked Shade, who you suspect to be Shadowblade. Once the Masked Shade is dead, search the body for proof of his identity.