Can't Complete Quest - Beneath the Veil

Beneath the Veil is part of the Stormsong Valley campaign questline in the Battle for Azeroth expansion. The Sagehold subzone where the quest objectives can become phased if you have started the Kul Tiran Allied Race questline but have not completed it. To resolve the issue, pick up the next quest in the Kul Tiran unlock questline and continue through the questline until you have completed it and unlocked the allied race. Doing so will fix the phasing in Stormsong Valley and allow you to complete Beneath the Veil.

For additional information about troubleshooting this questline, visit Wowhead's Stormsong Valley Troubleshooting Guide.