Red/Crimson Nichirin Is unlocked by getting 1000 Contribution,there is no rank required and no stats required.
You need to go to the Slayer HQ,you will then find a red key. If you have 1000 Contribution a prompt will show up asking "Do you want to buy ??? for 1k Contribution?"
If you say yes,a key named "Infinity Key" will be placed in your inventory.If you accept the key it will teleport you to a room with the Upper Moon 2
"Douma" inside,defeat the boss and press T after you defeat/decapitate the boss.
The Red/Crimsion Nichirin Increases your overall damage by 1.5x,it can also be stacked with the Demon Slayer Mark. The Red/Crimsion Nichirin has an active duration of 40 seconds, and a cooldown of 2 minutes. This cooldown is reset when your character is killed/reset.
The Red Crimson Nichirin reduces demon regeneration by 50%.
If you want to defeat him with a friend, you can’t. If you and your friend use the key, 2 ‘Doumas’ will appear, both attacking the nearest person.
Tips for killing Douma
- You should left/right dodge after you launch an attack since Douma will launch the ice attack after you hit him with forms like Flame Breathing 2nd Form or Thunder Breathing 2nd Form.
- If you're low just keep running.
- Get your hunger bar at least a half before entering the battle.
- Start with m1s at the start of the battle.
- Run around him , and attack with m1s, after you are finished run around him and then repeat, you can also use some moves while doing this, but make your you run as fast as you can when your move is finished.
- Keep walking around and hitting him, doing this the boss doesn't hit you and it is rare for him to use skill, you will cheese the boss, not needed an HYPER rank, it is not the fastest method but the most safe
- When low on hunger or HP, keep running and throwing in some 1st forms or something to slow Douma down.