Hello Devil Summoners! After countless hours, I finally think I've found an answer to defeating Lucifer! And with all my experience, I learned 4 fundamental points for this Boss.
1st point: You need a healer on your team. With a Boss as strong as this, it is not possible to defeat it without a descendant healer, especially with the Boss having 2 phases and 40 HP in total.
2nd point: use Thanatos as your DPS. In addition to being the most accessible, he is the strongest demon for isolated enemies, because of his hunting ability, and also because he has a base power of 9 points.
3rd point: Use Demeter as your healer. Of all the healers I saw, she is the most appropriate, mainly due to her ability to give 3 attack points to the ally, and recover all the health of the ally with less health.
4th point: the last kagutsuchi point... This is the point where I'm still experimenting, with those two demons in the party there's still 1 point left to spend, and as one more ally is never too much, I have two options to present to you <3
1st option, defensive: I would recommend Legion, defending Thanatos and attacking Lucifer when he dies. This was the party that brought me the closest to matching my life with his, but there was only one problem that made me lose, the amount of Thanatos' action points (the red squares) for an extra attack I couldn't defeat. it. So the strategy was simple, save that last point.
2nd option, offensive: Rakshasa, even though he is weak (1 life point) he is my main bet in this challenge, mainly because of two skills (Reaper and Double hit), according to my calculations (and if Lucifer doesn't stick a Morning Star in my face and not even attack before Rakshasa) Lucifer would have 3 life points when Rakshasa finished his second attack, leaving me with a question, Jab_Lao, how does the Reaper skill work? I think that even without this party, this skill will be of great help to the challenge. Fun fact: I'm not sure yet, but I think that if you only have one demon in front, Lucifer doesn't activate the Morning Star.
And that's it guys, I think I spent more than 24 hours in total playing this game, just so you can see how committed I am to solving this mystery, so I'm going back to my cave and wait for answers. And if he's invincible I'll be extremely angry lol.