As a skinwalker, you'd be able to take control of weakened opponents. Can never do so against bosses.
It may be an Ultimate class ability.
You take control, and you become the target for a while. You might even be able to progress several quests as that target.
You may or may not be able to keep that skin when transiting via any shrines, or swapping between instances or zones.
There may be changes to NPC behavior based on your skin, such as they may perceive you as that entity and treat you as such. As such, certain skins may cause Guards to be hostile towards you, or cause other NPCs to treat you like a fugitive. Allies of that skin may treat you as disguised. Higher class opponents will not be fooled, and will know there's a spell at play be it illusion or skinwalker, in which you're skinwalking.
When you become a character, you fully heal and have their resources, abilities, and weapons.
If you die while skinwalking, you drop their skin and are fully restored. You lose all your ultimate.
You can go into the character screen to drop the skin you are using.
You can immediately skinwalk into most basic NPCs. Some NPCs, like 1 bars, you may need to weaken, or reduce below a certain HP, before you can skinwalk into them.
You can never skinwalk a boss.
May add more later