Mark of Pain
The Mark of Pain is a Memory Stone found within the Hero's Grave. Upon being marked with this stone, you take double damage from every attack, and cannot heal at Save Shrines. This also applies to respawns, meaning that you will spawn at less than 1 heart, and have to either get your Echo back without taking damage or use the Emerald Bracelet to heal. Once the mark is inscribed on you, you cannot remove it, and it will stay with you until the end of the game.
Appearance
The Mark of Pain is a stone, with a circle and a dot enscribed in its face. Blood pours from the stone, symbolizing the sacrifice made to obtain it.
How to Acquire
After getting the Emerald Bracelet, go to the next room, ascend the steps, then go right (where you would find the Joyful Heart). Jump up, and grab onto the ledge you cannot see, then ascend to the gate that blocks this particular marking.
You cannot enter this gate unless you are at low health, so if your are healthy, throw yourself into the pit of spikes until the small pillars nearby glow red.
Enter the room, then inspect the candles, which will prompt the skeleton in the back to speak with you. It will offer you the Mark, to show your worthiness to the Goddess, and should you accept, you will be marked by it, never to be removed.