A second being resides within your body along with you. It manifests on you as a large dark purple mark that can move and change shape. It relies on you for its survival. At the same time, it offers you knowledge and other assistance, either of its own volition or because of your intertwined nature. The symbiote has its own personality and agenda, which might be at odds with yours. If you ignore the symbiote's desires, it might strive to interfere with you. There is no way to be rid of the symbiote while you have this Dark Gift. Even if you go to drastic lengths, such as severing the part of your body where the symbiote resides, it reappears on your body in another location at the next midnight.
Entwined Existence:
Your symbiote is a separate entity with its own physical form bound to yours. It isn't a separate creature and relies on you to survive. Its has ability scores of 14 in Intelligence, Wisdom, and Charisma. The symbiote can see and hear using your senses.
The symbiote speaks can telepathically speak to any creature you can see within 30 feet of you. It voice the creature hears can be your symbiotes or your voice. If it uses your voice, you hear the conversation. It doesn't need to share a language with the creature for it to understand the telepathic utterances, but the creature must be able to understand at least one language.
You gain proficiency in Perception as the symbiote notifies you of things you would have otherwise missed.
If you die, so does your symbiote. If you are subsequently returned to life, your symbiote revives as well.
Sustained Symbiosis:
Your symbiote has a vested interest in your survival and takes steps to ensure it. When you fail a saving throw, you can choose to have your symbiote expend one of your Hit Dice to roll it and add the number rolled to the saving throw, potentially turning the failure into a success. If it uses this feature on a death saving throw, you succeed on the save and regain 1 hit point regardless of the number rolled on the d20.
Once you succeed on a saving throw due to this trait, the symbiote can't use it again until you finish a long rest.
Symbiotic Agenda:
Your symbiote desires to be close to the Obelisk shards and it expects you to assist it in achieving its goals. How permissive or patient it is in resolving its agenda depends on its personality (determine by the DM). If you have an opportunity to advance its agenda and don't act on it, the symbiote can try to force your hand. You must succeed on a DC 14 Charisma saving throw or be charmed by the symbiote for 1d12 hours.
While charmed, you must try to follow the symbiote's commands. If you take damage that is not self-inflicted, you can repeat the saving throw, ending the effect on a success.