How do you blow up the portals?

[Beautiful Time]

I'm on the fifth island and have the bronze. I have no idea how to blow up any of the portals though, i just know how to get the knights and archers to attack. Can anyone offer any assisstance?

Many thanks.

[Silvi the Bun]

There's a building that spawns if your kingdom is 'wide' enough with a large bomb flag, You construct it and it'll get pushed by 3 builders, it will aslo be joined by knights and the entire thing will follow you to the right. The way it works is pretty awkward though, the band with bomb will follow you towards the portal but if you decide to go back they will just stand still where they got to.

After that you pay a few more coins to enter the bomb into portal and you pay coins inside portal to blow it up. Make sure to take coins with you into the portal so that you don't end up unable to light the fuse.