Primordial Blessing of Earth

You have received a boon from the Elemental Plane of Earth, perhaps from an Earth Elemental or a Dao. You gain the following benefits:

• Increase one ability score by 1, to a maximum of 20.
• You gain advantage on Constitution saving throws and ability checks.
• You learn the stoneskin spell. You can cast this spell once without expending a spell slot. Once you do so, you can’t cast the spell in this way again until you finish a long rest. You can also cast this spell using spell slots you have of the appropriate level.