The Sacred Heart is landmark in the Dimension of Death.
The immense Sacred Heart pumps the blood of immortality through the Dimension of Death. During the cataclysm, the heart had been injured and ceased to pump. Without the heart pumping, blood filled pools throughout the Dimension. When Connor balanced the Scales of Justice the heart was repaired and started beating again. Pumping the blood out of the pools, allowing him access to the Mold. When the Connor first encounter that Sacred Heart, he says" that is an immense heart" but after started beating he says "Zounds, this is indeed a heart!!" and he exactly believe this is a heart.