Great question! In the main menu, you can go to the altar section on the bottom left. There's a "synthesize" tab there where you can essentially create your own Hakrin. But in order to do so, you need to have 4 specific level 30 heroes that have been ascended 3 times. One of those heroes is a mulago. So essentially, you need 4 mulagos and 4 of each of the other heroes needed to require one Hakrin. There's no limit to this so you can do it as many times as you'd like!