Dungeons/Tombs , Cultivation/Martial Arts

Our mc, Seo Ju-Heon was betrayed by his boss who he worked for and even became a working dog for him to get a healing medicine/artifact for him and his comrades but instead gets betrayed and dies with his comrades. He travelled 15 years back in time with the help of a crow artifact(?) and decides to get revenge for him and his comrades while going into tombs and getting artifacts and also getting back his comrades and restores back their memories from their past selves.