The Spy

"The spy has already breached our defences. You see what he has done to our colleagues!? And worst of all... he could be any one of us! He could be in this very room! He could be YOU, he could be ME! He could even be- BLAM"

Spies are stealthy, but they do not camouflage themselves with leaves, mud or paint. They hide amongst the faceless masses, wear the identity of another like a veil and move unseen in plain sight.

Handy Disguise

Level 3: You can apply a disguise using a Disguise kit in only one minute. Creatures are unable to perceive through your disguise via magical means, to do so they must succeed on an Insight check versus a DC equal to 8 plus your Disguise kit modifier.

If you do not have proficiency in a Disguise kit you can exchange your proficiency in Thieves' tools for proficiency in a Disguise kit.

Improvised Assassination

 

Level 3: When you make an attack roll using an improvised weapon you gain the ability to use sneak attack on a melee attack so long as you do not have disadvantage on the roll. The weapon must deal piercing or slashing damage for this to take affect.

Backstab

Level 9: If you sneak attack a creature within 5ft that presumed you were an ally before the attack the attack deals additional damage equal to your rogue level. In addition, when you perform a backstab you can choose to forgo damage to stun the target until the end of your next turn. 

If you sneak attack the target as part of a backstab and choose non-lethal damage, you can force the target into a sleeping unconscious state so long as your single attack deals more than half the target's maximum hit points.

Counter-Spy

Level 13: You are able to see through the false forms of others. You gain 120ft of True Sight, allowing you to peer at a creature's true form.

Combat Mimicry

Level 17: When a creature makes an attack within 5ft of you you can use your reaction to instantly mimic the appearance and voice of the creature, this magical disguise lasts one minute. In addition, if you are damaged by a spell that targets you of second level or lower, you can cast the same spell at the same level without expending a spell slot any time within the next minute.