My theory is that other 18 kings & queens are sleeping in ice chamber and waiting to be free
Theres no way the WG doesn't have some aces/secret fighting force up their sleeve considering Luffy's alliance will be OP as fuck.
When shits starts to hit the fan really badly for Imu and the WG (which it will, considering HKs are dogshit), they will definitely use a trump card like the other 18 kings coming back.



