Copycat

Copycat rogues have figured out how to use magic to steal things that aren’t physical — the capabilities of others. These rogues are exceptionally creative, bending and twisting magical forces to replicate other creatures’ abilities.

Copycat

Starting at 3rd level, when a creature within 30 feet of you that you can see uses an ability other than a spell, you can immediately use your reaction to gain access to that ability yourself. You can use the ability in exactly the same way as the creature uses it, meaning you use it as if you had the same statistics as that creature. This effect lasts for one hour or until you use this feature again.

Additionally, you gain proficiency with the disguise kit.

Spell Snatch

Starting at 9th level, after a creature within 30 feet of you that you can see casts a spell, you can use an action before that creature’s next turn to make a Charisma (Performance) check against a DC equal to 10 + twice the spell’s base level. On a success, you gain access to that spell for 8 hours, but you can only cast it once with this feature during that time. When you cast the spell in this way, you cast it in exactly the same way the creature did, meaning you cast it as if you had the same statistics as that creature. 

Once you successfully gain access to a spell with this feature, you can’t use this feature again until you finish a long rest.

Magical Mimicry

Starting at 13th level, you can use magic to unerringly replicate sounds, and even make yourself appear to be different things.

You can use an action to make a Charisma (Performance) check to mimic a sound you have heard in the last hour, or to transform yourself into a Medium or smaller object that you have seen within 5 feet of you in the last hour.  A creature who is familiar with the sound or object you mimicked must succeed on an Intelligence (Investigation) check or Wisdom (Insight) check against the total of your roll to determine that the sound is not the same as the original, or that the object is not the same as the original. Otherwise, creatures who are not familiar with the original cannot tell that your mimicry is a fake.

While you are transformed as an object, your statistics remain the same, but you are only capable of using this feature to make sounds or transform into another object, and you must remain motionless. If you do anything else, you revert to your true form.

Permanence

Starting at 17th level, when you use your Copycat feature, the ability you gain access to is permanent, but you can only gain one permanent ability in this way at a time. You may also gain access to one additional ability by using Copycat, but that ability only lasts for one hour or until you replace it by using Copycat again.