Speedster

Speedsters go fast. That's usually what they're known for, but Speedsters can use such a commonly overlooked ability to great benefit in many other capacities.

Remarkably Agile

Starting at 3rd level, you are remarkably faster in combat. Your movement speed increases by 10 feet.

Additionally, you gain proficiency in the Acrobatics skill, if you do not already have it. Your proficiency bonus is doubled for any ability check you make that uses that proficiency.

Swift Stealth

Starting when you choose this archetype at 3rd level, your speed can serve to make you stealthier. If you take the Dash action, you have advantage on Dexterity (Stealth) checks until the start of your next turn.

Drive-by

Starting at 9th level, you can speed by enemies, causing quick bursts of harm before your opponents notice you. If you use your cunning action to Dash, you can make one additional melee weapon attack if you take the Attack action.

Flurry of Blades

At 13th level, you can momentarily enter bursts of extreme speed, attacking multiple targets in the blink of an eye. You can cast the steel wind strike spell, and when you do so, you can apply your Sneak Attack to one target, without needing advantage on the attack roll (all other rules for Sneak Attack still apply). Dexterity is your spellcasting ability modifier for this casting of the spell.

Once you use this feature, you cannot do so again until you finish a long rest.

Quick Feet

Also at 13th level, your movement speed increases by 10 feet again.

Inscrutable Agility

Starting at 17th level, you are so remarkably agile that almost all restraints simply cannot hold you. You are always considered to be under the effects of a Freedom of Movement spell.