Deathless are rather tough, but retain some of their other traits.
+2 to your constitution and +1 to any other ability score of your choice.

You count as medium

Your walking speed is 30 feet

If damage reduces the you to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the you drops to 1 hit point instead.

You may add your constitution modifier to death saving throws. Furthermore, anytime you roll a successful death saving throw that success counts as critical. 24 hours after death you may roll a d20, on a 1 you come back from the dead with half of your hit points. This trait is cancelled for one minute if the damage you suffered was a source of radiant or from critical damage.

You are considered undead for effects such as turn
undead but not any healing effects that exclude undead. You are immune to disease and
the poisoned condition, and you have resistance to poison
damage. You do not need to eat or breathe, but you can ingest
food or drink if you wish. Instead of sleeping, you enter an
inactive state for 4 hours each day. You do not dream in this state,
but resting in this way is otherwise identical to sleeping.
Magically induced sleep can cause you to enter this inactive state

You have darkvision for up to 60ft

You can speak read and write common and one other language of your choice.