Diamonds are one of several Artifact currencies that can be earned within the Underworld. Along with Titan Blood and Ambrosia, they are a resource obtained via bounties. They can be used to purchase higher tier upgrades from the House Contractor, such as a Music Stand for listening to music, progressing character favors, or bonuses for picking up resources in escape attempts.
||'Among the hardest, most bedazzling of substances born underneath the earth, the diamond nonetheless has somewhat of a stately manner, colorless and stoic next to all the multicolored stones with which it coexists. But what it arguably lacks in outward beauty it makes up for with its uses in the sprawling industry of death which Master Hades oversees. Within the Master's House, the diamond always holds a special place; its hardness, helping excavate the stone and carve out all the likenesses and monuments encapsulating many ages past; its shimmering facets, hewn a certain way, absorbing little bits of light that can remind even an ancient shade of what it meant and what it means to live.'
Diamonds can be obtained by completing some prophecies from the Fated List of Minor Prophecies. They can also be obtained via trades with the Wretched Broker.
Diamonds are primarily earned by beating the Lernaean Bone Hydra and collecting a Bounty for escaping Asphodel. This means Zagreus must defeat the Bone Hydra at a higher Heat level than previous victories using the Pact of Punishment.
Occasionally, a Diamond can also be purchased from Charon's shop in the Temple of Styx for 1000 .
Poseidon's boon Sunken Treasure also has a 0.03% chance of dropping a Diamond.
Fishing in Chaos Gates is also a way of obtaining Diamonds. Although it's very rare to catch a fish rewarding a Diamond.