That is not what I expected from closing the portals. I know that they are made of mana as they can easily tear through reality and the only things that can do that are either the mana itself or some sort of monster that is capable of tearing through space and reality.
But absorbing the portal and using the mana from it as yours is not something I am expecting at all. Is that the main reason why back in the real world, my max mana pool has increased significantly? That shouldn't be the case since I didn't even absorb the mana from that portal, I just overloaded it with magic skills, forcing it to close on its own.
But who knows, things might be different in the game and reality or I just absorbed it without knowing.