The Lord of Pain only takes damage while you're standing in the Ring of Pain. As soon as you step into the Ring of Pain, you're inflicted with Exacting Punishment. It begins with 20 increments and counts down as long as you stay within the ring. If it reaches 0, you die. Once you leave the ring to remove Exacting Punishment, you receive Lasting Pain. If you re-enter the Ring of Pain before Lasting Pain expires, you die. While outside the ring, you'll build increments of Brink of Death which can be cleared by entering and leaving the Ring of Pain. By staying outside the ring only as long as needed for Lasting Pain to expire, you can keep the increments of Brink of Death low.