So what are we thinking here with the 19 swords?
Is it just a vow/promise not to sit on the throne or was there like DF powers involved/something more concrete that makes the vow impossible/very difficult to break?
If it's the latter I can see Imu being Lili or a direct descendant. "Returned to Alabasta" so didn't have to take the vow but stayed there and become the Queen/King of the world for some reason. Which explains why she never made it to Alabasta.
Or was it just Imu taking her out because she didn't take the vow and now is getting rid of her/her brothers? descendants that they are looking into it too much.
The latter doesn't make as much sense since 19 swords would suggest Imu(or his/her ancestor) took the vow so it's just meaningless and would be no reason to take Lili out because of that.