You have a bone devil lurking somewhere in your family tree this grants you the following benefits.

• You get a +1 to your constitution score
• You gain darkvision up to 30 feet
• You gain access to the Fiendish Carapace transformation, lasting up to 10 minutes. You can transform a number of times equal to your Con modifier, you regain uses after a long rest. Transforming causes any equipment you are wearing to merge into your form similar to wild shaping. The transformation looks like a exoskeleton made of human bone.

Fiendish Carapace

• Your darkvision increases to 60 feet and magical darkness doesn't impede it.
• Your unarmored AC if equal to 10 + Con mod + proficiency bonus.
• Your unarmed strikes deal an additional 1d6 poison damage.The poison damage increases when you reach certain levels, increasing to 2d6 at 5th level, 3d6 at 10th level, and 4d6 at 15th level.