Before anyone says this was the fifth time in a row, the citadel was in peace for a while so this was going to happen

Remember that pink guy that vegeta fought?
Citadel is never safe

Literally only me and you remember him.

G: hey, I didn’t do it. My portals are purple.

B: I’m going in

just, put a big concrete slab on the front and back

that would not work due to the known properties of the portal

well then put it in a big box

again, that wouldn't work

well then create a black hole so there's an epic fight before everyone dies

that would take too much time

maybe if you ignore it for long enough then it'll leave because nothing is feeding it

how does one feed a portal

throwing something inside