Stage 1 - A Scarlet Abyss

• Noel has sent you to investigate an anomaly near Randall. Meanwhile, a fiery warrior can be seen in the distance...
• Energy cost: 10
• Battles: 5

Stage 2 - The Maw of Darkness

• As you explore the building, blood is thick in the air. Everyone around you seems to be fighting each other! What is going on?
• Energy Cost: 20
• Battles: 5

Stage 3 - A Dark Resurrection

• Death stalks the halls as you reach the center of this madness; the silence is overpowering. What insanity will you meet here?
• Energy Cost: 30
• Battles: 5
• Continues unavailable - you cannot gem to revive units
• First time clear reward: 1 Gem, 6* Rugal Bernstein (Lord, random type was a bug)

Stage 3 notes

• Terry on wave 3. Immune to crit damage. Dies fairly easily to spark nuke squads. BB drains at certain points.
• Rugal is completely immune to crit damage (can still be critted, but no damage bonus). Can be Injured and Weakened.
• Rugal will do a heavy nuke AoE curse every 4 turns (after passing 75% HP threshold?).
• Rugal occasionally gains DEF Ignore
• Constant BC fill rate debuff during Rugal and Terry fights. Seems to affect all BC sources.
• Below 10% HP, Rugal will gain 100% mitigation. Can be skipped if you nuke him from 11% to 0% in one turn. He will survive via angel idol and heal to 11% again, but you can still win after that with another turn of nuking.
• Some turns after he gains 100% mitigation, he will nuke/buff wipe your squad. Potentially survivable via angel idol passives (Juno LS, Selena ES, etc) but otherwise a gauranteed squad wipe.
  • Nuke can apparently be prevented with Kyo's UBB if you wait for Rugal to get an HC drop rate debuff
  • If you get Rugal to 1 or 2% you may be able to kill him with DoT from Kyo during his 100% mitigation, but the time limit is too low to do this reliably. It's also unknown whether it'll interrupt his nuke.

Rugal Bernstein will evolve into a 7* unit, Omega Rugal (His 7* name was changed overnight).
Evo mats: Dark Mecha Totem, Miracle Totem, Dark Totem, Dark Totem, Dark Idol.

Discuss encounters, strategies, etc.

Remember that according to Gumi's pre-announcement, you will need Kyo Kusanagi in your squad to attempt the final stage.

Update on the random type Rugal:

Gumi have just recently addressed this on their official forums:

[ADVISORY]

Attention,

Some Summoners have succeeded in Scarlet Abyss Tournament and have captured Omega Rugal from First Time Clear Rewards. However, Some Omega Rugal type were not in Lord Type. We apologize for the inconvenience that this has caused you.

Our team has already fixed this issue as of July 29, 8:06 PST and it is now safe to enter the Scarlet Abyss Tournament and rest assured that Summoners can now obtain a Lord Type Omega Rugal as a First Time Clear Reward.

For Summoners who have a non-Lord type Omega Rugal, we strongly suggest to leave it as it is for now as our team will set it back to Lord Type within 3-5 days.

Again we apologize for the inconvenience and we thank you for your understanding and patience.

Thanks to /u/paulo_pupim for posting about this in this thread.