Weapon dancers are masters in combat against multiple opponents. They juggle their weapons to surprise and disorient their enemies and strike with precise. They are not afraid to dive into crowd of enemies, because all advantages they will, probably, have are gone and turned against them. They are like a tornado which destroys everything around them. An easy way to tell that you see a weapon dancer is to see how many different weapons a person carry on him. 

Weapon belts

At level 3 you can choose up to 7 different melee weapons. Now you can change your weapon in combat between those without spending any action. Also you gain an ability that grants you +1 to attack and damage roll for weapon that you choose by this ability until you make a successful attack with it. 

At level 10 you gain +2 to attack and damage roll and +3 at level 18.

Crowd control

At level 7 you are not provoking opportunity attack while you are in melee range of any other enemy creature. Also, at your turn, if you make two melee weapon attacks on two different targets, you can make another one melee weapon attack. If you are targeting a third different creature this attack you will gain an advantage.

At level 10, enemies will not have an advantage by surrounding you.

Weapon expertise

At level 10, you can choose 2 weapon type* you gain expertise in those types.

At level 15 and 18, you choose another weapon type*  

* – I believe that every weapon, even homebrew, could be considered as some type of weapon which has been listed in PHB at page 149. So "type" in this ability mean one of weapons in the list and any other variants of it. 

Perfect grip

At level 15, your number of reactions increases to 2. Also, now you ignore weapon's feature "two handed"  and any weapon that you handle is not having "throwable" now gain weapon's feature "throwable" (20/40).

Deadly precise

At level 18, after you land a critical hit or kill an enemy, you gain back all advantages from "Weapon belts" ability which you were spent in this fight. Also, once per your turn after you land a critical hit or kill an enemy you can make another attack.