The Heart Crystal mod allows you to mine heart crystals, which are found deep underground. When you mine one, you can eat it to gain one heart of maximum health!
Finding a heart crystal in a cave.
Heart lanterns provide light and charge up until you can absorb health by right-clicking.
Some hearts are kept and some are lost on death, depending on the config.
1.1 adds in a new model, heart lanterns and heart shards, along with a magnitude of config and some new/tweaked mechanics.
1.1.1 adds an option to revert back to the old heart crystal model used in 1.0.