Due to your magical reanimation, your Wisdom increases by two and you Dexterity by one.

You can see up to 120 feet in Dim Light as if it were bright light.  This does not affect darkness, magical or otherwise.

You are already dead, and cannot die of old age.  

You do not require food or rest. Instead of taking long rests, you enter a state of regeneration for 6 hours during which you are aware of your surroundings, but can not take actions without needing to restart the process. You do not gain Exhaustion if you do not rest. You are immune to affects that would age you or affect flesh, which you lack.  This does not include damage variations.  You are immune to Poison damage from nonmagical sources.

You can cast Speak with Dead at will, without material or verbal components. You can telepathically communicate with any creature you are aware of within 60 feet of you, unless this is blocked by an affect of terrain or magic, at the DM's discretion. You must share a language for this to work, and cannot speak otherwise. You can hear as normal.

You automatically succeed on stealth checks while immobile and prone in an area it makes sense for a skeleton to be, unless the observer is under the effect of a Detect Magic spell or similar affect.

When casting a spell, you can choose to cast with telepathy instead of verbal components.  This only works as long as you can use your other telepathic capabilities.

You speak Common and one other language of your choice, usually related to your past life.