Thikreen have 4 arms. The secondary set can use Light weapons. Note that having 4 arms, each holding a Dagger or other light weapon doesn't inherently grant any additional attacks.

The best combo I have come up with is using 5.5 weapon mastery ruleson a Berserker Barb, and a 2h weapon with some desirable property like Cleave in your Primary arms, and Scimitars in your secondary arms. After level 5, with attack action you can make 1 attack with your big weapon, Cleave attack if you hit, then 1 attack with the secondary arms Scimitar, then an attack from Nick as part of that same attack action, then a bonus action attack with scimitar. STR bonus on first 2 attacks, +2 Rage bonus on all 5 attacks, +2d6 damage on first hit when Reckless, which you should always use.