Soul Hackers 2

A Sabbath is this games version of All-Out attacks you can do in Persona games. Each time you hit an enemy weakness, it will add (at least) one to the stack count. At the end of the party turn, this results in a Sabbath that damages all enemies (unless you have used the Commander Skill Damage Condenser, then it's single target). The stack can only grow to as many demons as you currently have with you. Unlike in Persona, there's no knockdown effect, so you don't have to hit every enemy in a turn to get a sabbath, you always get one as long as the stack count is present.

As this is something you should be doing most of the time (unless you can't/are conserving your MP for stronger enemies), this should come through normal gameplay. Depending on how much side content and Soul Matrix you do, you can get this before clearing the Central Line no problem unless you are actvely avoiding it.