The average assassin is extremely dexterous but you are the most dexterous Your entire ability is to execute suicide missions and get out like nothing happened. you can be in a very enclosed space and still be able to get out without any issue, their nothing in the whole world that can pin you down in a single spot. Or even trap you as matter of fact you'll always escape somehow

Stunning agility

You have a knack for escaping and evading scenarios when you need to. Whenever you make a saving throw of any kind add your dexterity modifier +2 to the roll. Additionally if you roll for a saving throw regardless if you succeed you can move 10ft in any direction. You get a climb speed equal to your walking speed if you already have a climb speed add 30 ft to it. You can fit an another creatures space and you can fit in small spaces or objects.

Risk Taker

The more you continue to escape the risky you get. Starting at 9th level whenever at an attack hits you can roll 1d8+dex modifier and subtract that much damage from the hit. You can do this an amount of times equal to your proficiency bonus. Additionally you don't provoke opportunity attacks and At the start of combat roll 3d20 for all of that combat you can replace one of your rolls with one of those dice rolls you can use this any amount of time equal to your proficiency bonus. You regain all expended uses of this feature on a short or long rest.

Grand Escape

As you learn every single thing about escaping you learn one of the greatest tools a Escape artist can have. When you reach 13th level you learn your grand escape. once per long rest you can choose any 3 saving throws of you choosing (like constitution, dexterity, or charisma) and add your dexterity and charisma modifier to that and add the dexterity and charisma modifiers of your one of your allies to help you succeed this lasts for 1 minute. Additionally you can use your reaction too choose one attack hitting you or an ally and half that damage.

Success Mastery

You can use your mastery of all forms of escape to empower your allies and yourself protecting them from all thing. Starting at 17th level whenever you succeed a saving throw you can make two other allies automatically succeed the saving throw. additionally you can give yourself and your allies temporary hp equal to all of your dexterity and charisma modifiers combined you can use this feature Twice per long rest. finally whenever you roll a saving throw you can move 20ft in any direction 30ft if your moving towards an ally.