After the player has conversed with Sisyphus a number of times, Zagreus becomes able to have "conversations" with Bouldy and can even gift him Nectar. Thereafter, he can be gifted Nectar once per escape attempt if Sisyphus' room is encountered. Doing so rewards the player with the Heart of Stone boon, which rewards a random buff when acquired. Though the boon offers modest stat increases it can be useful if the player has excess Nectar, as it is the only mid-run benefit one can receive by spending Nectar. The boon can bestow one of the following effects:
List
| Name | Description | Effect | Note |
|---|---|---|---|
 Heart of Stone |
You believe in Bouldy, and Bouldy believes in you. | Damage Reduction: +1-5% | |
Heart of Stone |
You believe in Bouldy, and Bouldy believes in you. | Attack Damage Bonus: +1-5% | |
Heart of Stone |
You believe in Bouldy, and Bouldy believes in you. | Special Damage Bonus: +1-5% | |
Heart of Stone |
You believe in Bouldy, and Bouldy believes in you. | Cast Damage Bonus: +1-10% | |
Heart of Stone |
You believe in Bouldy, and Bouldy believes in you. | Movement Speed Bonus: +1-10% | |
Heart of Stone |
You believe in Bouldy, and Bouldy believes in you. |  Bonus: +1-10%
|
|
Heart of Stone |
You do not know if you believe in Bouldy... | Ambiguity Bonus: +2% | "Ambiguity Bonus" appears to do nothing at all for Zagreus' abilities. |