The abandoned cave is Elden Ring Dungeon located in Calida and boss here falls the Golden Scarab.
You can enter the dungeon from the Smoldering Wall of Grace, and the entrance to the dungeon is in the east. Head east from the Place of Grace. You can avoid all the enemies here by following the firewall until you reach a gorge and then head south. You should see a broken tree spanning the chasm and you need to use it as a bridge to get through. Look at the screenshots above to see the exact location.
Once inside, you can activate the abandoned cave before continuing. This dungeon isn’t particularly large, but it has plenty of Scarlet Rot pools, as well as poison-spitting enemies. You should also watch out for geysers, as they will damage you even if they don’t erupt. Once you’re done, you’ll need to fight a boss – a pair of Pure Rot Knights. Kill the spear knight first, as he is much more dangerous, then deal with the sickle knight. Once both are defeated, you will be rewarded with the Golden Scarab Talisman.