Skeletons are commonly raised as mindless servants or soldiers by potent necromancers. They may also be the result of a curse that prevents a soul from truly passing on to the afterlife; perhaps thieving cursed valuables, or wronging a powerful being. Skeletons are often the remains of a mortal from decades or even centuries past, and their remains will reflect that. They might be nothing but dry bones cobbled back together with necrotic energy, or perhaps they still have vestiges of rotting or desiccated flesh dangling from their forms. The death of the master that raised them, a reconciliation or cleansing of the curse, can end up awakening a skeleton from its mindless service instead of returning it to death.
Skeletons often experience the most confusion and disconnection with their previous life - they retain only fragments of memory that flow through their hollow skulls. The length of their death is reflected in their state of decomposition, which means that there is a great deal of time and distance from their mortal life. Skeletons are the least likely to try and re-engage in their old life, and are far more likely to strike out on adventure when they are freed from servitude.
Ability Score Increase
Your Constitution score increases by 2. Choose either your Dexterity or Charisma score to increase by 2.
Skeletal Structure
Your lack of significant flesh is both a boon and a curse. Piercing weapons are less effective against you, but you have no fleshy padding to protect your dry bones from bludgeoning damage. You gain resistance to piercing damage, but are vulnerable to bludgeoning damage.
False Appearance
As a bonus action, you can reduce yourself to a pile of bones. While in this state, you are rendered prone, and you appear dead to all outward inspection and to spells used to determine your status. While in this state, you are blinded and incapacitated, and your speed drops to 0. You gain resistance to all damage except psychic damage, you have disadvantage on Dexterity saving throws, you can’t take reactions, and the only action you can take is an action to reassemble yourself.
Bone Pick
Your bony, skeletal hands can be used as simple tools. You gain proficiency with them, and can use them as Thieves Tools and Tinker's Tools.
Real Backbone
Starting at 5th level, the necrotic energies that stitch you together in place of muscles keep you from from falling easily in battle. When you are reduced to 0 hit points and not killed outright, you can drop to 1 hit point instead. When this happens, you collapse into a pile of bones and are subject to all of the conditions of your False Appearance feature. You can use this feature a number of times equal to your Constitution modifier. This ability recharges after a long rest.
Ghastly Ambusher
Starting at 8th level, as a bonus action you can reassemble yourself and rise from a pile of bones surprising your enemies. If this is the first round of combat, any creature within 10 feet of you is considered automatically surprised. If this happens during combat, any creature within 10 feet of you that can see you must make a Wisdom saving throw equal to 8 + your proficiency bonus + your Charisma modifier. On a failure, they are stunned until the end of your next turn. On a success, they are not stunned but are momentarily distracted and grant advantage to the next melee attack against them from your allies before the start of your next turn.
If a target is within 5 feet and not facing the you, they are unaware of your presence. This grants you advantage against them until the end of your next turn. If you hit this target unawares, treat it as a critical hit.
You can use this feature a number of times equal to your Charisma modifier, and regain all uses after a long rest.
Evasion
Starting at 11th level, When you are subjected to an effect, such as a wizard's fireball or a dragonborn's breath weapon, that allows you to make a Dexterity saving throw to take only half damage, you instead take no damage if you succeed on the saving throw, and only half damage if you fail.