You must earn a Sanctum Medal through combat in Theobomos. Collect evidence of your prowess and take it to Dairos.
Step 1. Talk with DairosAn Abyss contribution recordkeeper in the west room of Protectors Hall in Sanctum. He is modest and reticent..
Step 2. Take Theobomos DeathmarkRefers to the Bloodwing’s Wings, Sylphen Saliva, Hornskull’s Tongue, and Abex Horn you obtained from hunting Cave Bloodwing, Forktail Sylphen, Thornback Hornskull, Sand Tongue Hornskull, and Hillock Abex. to Dairos. (You need to collect: Bloodwing Wings)