Etrian Odyssey V - Eternal Tyrant (Advanced) (One Hit Kill)

Eternal Tyrant doesn't have a conditional loot so you can defeat him without thinking about it.

Party: (Therian) Impact Brawler - (Therian) Blade Dancer - (Earthlain) Deathguard / (Celestrian) Spirit Evoker - (Brouni) Divine Herald
This strategy revolves around the usage of Impact Brawler's Heavenly Aid - Death's Edge combo which deals absurd damage and potentially kill the boss in one hit. When I played this game a year ago I tried this strategy against the final superboss of the game, but recently I just wondered if the strategy also works on the main story's final boss too. Therefore I adjusted the strategy and finally did it.


Several notes about the battle:
This battle has luck dependant only on the first turn. When everything goes according to the plan on the first turn, it's not too long before you kill the boss.

Assuming all characters stay healthy and can serve their best role all the time, the battle should go like this:
Impact Brawler: Overexertion → Heavenly Aid → Death's Edge
Blade Dancer: Armor Pierce / Sleep Gas → Bravant → High Ground
Deathguard: Sleep Gas / Wilting Miasma → Eroding Miasma → Defend
Spirit Evoker: Sleep Gas / Wraith Cry → Wraith Cry / Defend → Defend
Divine Herald: Aegis Shield / Superspeed + Vitality Prayer → Medica IV → Defend (or toss Heavenly Gift for more EXP if necessary)

Before the battle
You have to make sure Impact Brawler's HP is originally even, and after being multiplied by 1.4, the number is still even and less than 500. For example 356 * 1.4 = 498 matches the criteria, but 354 * 1.4 = 495 doesn't match. This will be explained later.

Turn 1
The main objective of this turn is to tank all damage (Aegis Shield) or go before the boss (Superspeed) and put him to sleep by tossing Sleep Gas. Blade Dancer can also perform Armor Pierce if the other two people have higher LUC that results in better chance to inflict Sleep. In this video I had to skip Armor Pierce since the other two characters had no luck to inflict Sleep to the boss. Wraith Cry can be done on the first turn too, but if you don't, just pray that the Wraith doesn't attack the boss. Deathguard can perform Wilting Miasma if this character has Miasma Armor at the start of battle so that this character goes before the others. Divine Herald's Vitality Prayer must activate before Overexertion. This can be done by learning Cardio and Prayer Mastery while Impact Brawler avoids any AGI booster skills. This is vital since later you'll put another ATK buff to Impact Brawler, which overrides the first buff in the slot.

Turn 2
In this turn Impact Brawler will cast Heavenly Aid while Divine Herald tosses Medica IV. Remember about the note about Impact Brawler's HP above? Maxed Vitality Prayer multiplies maximum HP by 1.4, and Medica IV heals 500 HP. Heavenly Aid has a quirk that if the user starts at 1 HP and fully restores their HP at that turn, the amount of magnification is close to 4 times. Therefore, you need to make sure the number is even and as close as 500 but not beyond that. The other party members just provide the necessary buffs / debuffs to the boss.

Turn 3
This is the final turn where Blade Dancer casts High Ground and Impact Brawler performs Death's Edge. The former should activate before the latter. High Ground has higher action speed than Death's Edge, but in order to activate it faster, Blade Dancer should learn all AGI booster skills while Impact Brawler should avoid all of them. If everything goes well, Impact Brawler now has Overexertion + Bravant + High Ground, the boss falls asleep and has either two or three DEF debuffs, and the resulting damage will one hit kill the boss.

Turn 4 (if the boss is still alive)
If you only dealt about 34,000 damage last turn, Impact Brawler can perform another Death's Edge whereas Divine Herald should perform Heaven's Gift so that Death's Edge can activate before the boss acts and wipe out his remaining health.


Notice that in this video the damage can be pushed further by Armor Pierce, but doing that would not become the true "One Hit Kill".


0:00 Setup
1:30 Interlude
2:34 Battle