This guide shows the complete walkthrough for Sainted Hero’s Grave in Elden Ring. This dungeon is in Altus Plateau at the location marked in the pictures below.
After entering the dungeon, take the elevator down to the Site of Grace. Here you will find a Stonesword door as shown below. you will find Crimson Seed Talisman behind this stonesword door. Now take the path on the left side as shown below.
As you proceed, you will see two paths ahead as marked in the picture below. If you take path 1, you will find a Grave Glovewort  underneath the stairs, but you will have to fight a giant spider. If you take path 2, you will find a golden seal on the floor as shown in the second picture below. Lure the shadow monsters to this seal to kill them. Both the paths will merge here.
Now as you process, you will find two more shadow monsters as shown below. Run past them and go to the right side to find another golden seal on the floor. Lure the shadow monsters to the seal to kill them. Now proceed ahead through the path on the east side.
As you proceed, you will reach a room with a collapsable floor. There is a Leyndell Soldier Ashes or a corpse in this room. After collecting the ashes, walk to the center of the room for the floor to collapse.
You will fall down on another Golden Seal. Lure the shadow monsters here to the seal and kill them. Then pull the lever as shown in the picture below to open the door ahead.
In the next room, you will find blades moving up and down. Stand on the blade to reach the platform above on the left side as shown in the pictures below.
Proceed ahead and you will reach a Stonesword Door as shown in the picture below. You will find a Grave Glovewort  and Dragoncrest Shield Talisman +1 behind this door. Now climb up the stairs and go ahead and you will eventually reach the room with the moving blades.
Proceed ahead in the room with the moving blades, and you will find a locked door. There is a ladder inside a nook on the right side of the locked door as shown in the picture below. Climb up the ladder.
After climbing up the leader, go right and you will reach a giant shadow monster as shown below. In this room, you will find a Ghost Glovewort .
Lure the shadow monster out of the room and then jump down on the right side to reach the room with the moving blades. Lure the shadow monster back to the golden seal as shown in the pictures below. Once the shadow monster touches the golden seal you will be able to kill it. This will open the locked door. proceed ahead to reach the Ancient Hero of Zamor boss. On killing it, you will get Ancient Dragon Knight Kristoff ashes.