Your undead body makes you especially resilient to damage, and your original body is still there so what you where good at in life you will still be good at in death-er undeath. You have +2 to constitution and +1 to any other stat of your choice. 

Your body is trapped inside a magic item that you picked up at some point in life, Upon death your soul was shot from your corpse and put into the item. Upon character creation you will start with a magic item of your choice, work with your DM during the creation process to make sure they are ok with what item you are starting with. 

Your body is effective but its not permanent. Upon reach 0 Hit Points your body disintegrates and your magic item will be left on the ground. This is now your character, should the chosen magic item be destroyed or the curse is removed in this state, your soul is released and you are dead. But fear not you can directly communicate with any creature that understands at least one language that comes into direct contact with it. 

Once a humanoid corpse comes into contact with your item, the possession begins and after a period of 10min you will be transferred into the new body, you take the new body size and your initial features (be they  dragonborne, gnome, grung, etc.) visually start to appear on the new host's body. 

If your item is attuned by a living humanoid while your soul rests inside it, you are able to fight for control of the body while you are attached. They are henceforth unable to release or remove the item as it is cursed. Roll a contested charisma check against the creature upon success you take over the body for 1D4 hours. This is something you may do once every 24 hours. If the creature dies at any point while they are attuned to your item you take control of the body as described in the previous paragraph. 

You are quite obviously undead, not only do you probably smell pretty bad you body will start falling apart after a while. While you could be anything from a schoolboy who unfortunately was trapped inside a cursed lunch box to an incompetent Litch who broke their phylactery and is now trapped inside the average person only sees a horriable undead that is probably wanting to eat their flesh or something. On the plus you are good at intimidating because of your gruesome appearance, on the minus nobody is going to want to listen to you insist, "trust me". You gain advantage on Intimidation rolls and disadvantage on persuasion rolls. 

Undead don't sleep, that's the reality of it. So unfortunately after a long day of adventuring you can't exactly curl up in your bead with your favorite Teddy Owlbear and get your 40 winks. But on the plus side you can keep doing some minor tasks while you recharge the ol' brain batteries. You can do light tasks during a long rest such as keep watch, sharpen a weapon or 2, or simply stare off into space longing for a time when you could still eat a burger (well you can still eat but you can't taste or swallow or get anything from it but i digress). 

Your undead body is very special, healing magic dosen't seem to do much for you, but you have found that magics that are usually desighned specifically to damage the body seem to do the oppisite to you. When you would take necrotic damage you heal half much instead but you are unable to heal through healing spells

You speak Common and two additional language of your choice