When consumed, it increases your maximum health by one heart but will make it appear as if you are being damaged. You may only use a total of 10 Shards of Life, making your maximum health 40 (every heart is two points). However, in the 1.10.2 build, these are found all throughout the dungeons, are only stackable to 4, and do not increase health. instead, they give a regeneration effect similar to healing stones.
Gilded Games has said that they will be making the Shard of Life even harder to get and that players can now use more than 10 on a single character.
Shard of Life's data values are:
Shard of Life
4131 (dec), 1023 (hex), 0001000000100011 (bin)
Issues relating to Shard of Life item are maintained on the bug tracker. Report issues for Shard of Life there.