The demon starts with 2 knowledge points. Knowledge points drop frequently. There are many minor artifacts that grant knowledge, as well as major ones.
Now, Valafar can place portals anywhere and change the exits and entrances as he pleases, at any distance from each other.
The only limitation is that the entrance and exit can be different colors.
Even so, the demon's mana isn't unlimited, and you still need 60 mana.
Also: a bug has been noticed with Kujin. When purchasing a hero, demons arrive at a rate of 1 per second. Isn't that a bit much?
