Quicksilver

You have dedicated yourself to the ancient proverb more is better, where in this case the "more" is attacks. With a weapon in each hand your movements will be just as swift as your enemies demise. 

Blur of Steel

3𝑟𝑑-𝑙𝑒𝑣𝑒𝑙 𝑄𝑢𝑖𝑐𝑘𝑠𝑖𝑙𝑣𝑒𝑟 𝐹𝑒𝑎𝑡𝑢𝑟𝑒

Your nimble maneuvers let you make attacks others can barely perceive.  You can now use the Nick weapon mastery up to two times per turn.

Offhand Expert

7𝘵𝘩-𝘭𝘦𝘷𝘦𝘭 𝘘𝘶𝘪𝘤𝘬𝘴𝘪𝘭𝘷𝘦𝘳 𝘍𝘦𝘢𝘵𝘶𝘳𝘦

Your duel-wielded has given your offhanded attacks more power behind them. Your offhand weapon attacks now add half the ability score modifier (rounded up) to their damage roll. If the value is negative, it is not added. This feature also applies to offhand weapon attacks made with the Nick weapon .

Rapid Strikes

10𝘵𝘩-𝘭𝘦𝘷𝘦𝘭 𝘘𝘶𝘪𝘤𝘬𝘴𝘪𝘭𝘷𝘦𝘳 𝘍𝘦𝘢𝘵𝘶𝘳𝘦

Your quick mind lets you do more in an instant than others can do in seconds. When you make an offhand weapon attack with your bonus action, you can make another offhand weapon attack with that same action.

Faster!

15𝘵𝘩-𝘭𝘦𝘷𝘦𝘭 𝘘𝘶𝘪𝘤𝘬𝘴𝘪𝘭𝘷𝘦𝘳 𝘍𝘦𝘢𝘵𝘶𝘳𝘦

Your need for a speed allows you to occasionally attack so fast it's as if two strikes are one. Once per encounter, when you use the Nick weapon mastery, you can make two offhand weapon attacks as part of it.

Light-Speed Strikes

18𝘵𝘩-𝘓𝘦𝘷𝘦𝘭 𝘘𝘶𝘪𝘤𝘬𝘴𝘪𝘭𝘷𝘦𝘳 𝘍𝘦𝘢𝘵𝘶𝘳𝘦

You now attack fast enough for your weapon to turn into just a blur of color. When you make a offhand weapon attack using your bonus action, you can make two more offhand weapon attacks as part of that action.