Tired of repeatedly explaining the first boss to players? Honestly, a written guide is way more useful than just a PoV video that doesn't break things down.
Here's a quick How To Guide for beating the first bosses in Prometun H. There's different methods, but this one is straightforward and minimizes players getting pulled. I've skipped the details for what the Main Tank should do.
Every phase, the boss gets tougher, hits harder, and influences how many people need to stack or avoid those "losing rationalities" moments.
Group composition: 1 Main Tank, 1 Cleric, 4 DPS (make sure at least one can speak on voice chat)
1) Yarkhan - Initial Setup
Pick someone for tanking Raging Yarkhan – they should pack a punch and self-heal a bit. (Most classes work).
Stand as shown in the image, near that chain in the room opposite side from Yarkhan’s spawn, but slightly off-center to make it easier. You shouldn't have to move from there the whole fight. Also, you’ll need to call out Poison Tail to your team.

2. Barkhan
Your Main Tank (Blue Mark) waits by the wall till Yarkhan's at 75% health. That's when Barkhan appears. The Cleric (in Burgundy) needs to stay positioned so they can heal the tank and Yarkhan’s tank if necessary.

3. Poison Tail
Yarkhan likes to dish out Poison Tail x2, either hitting 2 different players or one twice. Have Yarkhan’s tank call this out (way easier over TS/Discord).
Poisoned folks move to the Green Spot in the corner.
*Poisoned players can keep whacking away at Barkhan.
All non-poisoned players should move to where Yarkhan gets tanked and STACK up.

4. Poison Tail - Stacking + Pull
Non-poisoned need to stack. Stacking’s important since Yarkhan casts an attack that shares damage across everyone. The longer it takes to kill them, the more people need to stack. (It's a 15m range, so outside stack or with poison, you'll suffer full damage). While stacking, keep hitting Yarkhan (top DPS should help from Barkhan).
Right after the attack, Barkhan will yank everyone in. If you stack where shown, you won’t get pulled (or use a resist skill).

5. Losing Rationality
After everyone's pulled in, Losing Rationality is next. (if stacking right and not pulled, keep pounding Yarkhan then focus on Barkhan). Cleric should dispel debuffs on pulled players since their speed’s dropped. Keep clear of the Losing Rationality skill (15m effect).

6. Get Back in Position
Once 'Losing Rationality' is done (happens 1-2 times each phase), resume hitting Barkhan. Both bosses gotta drop together (you have around 30 secs to take out the 2nd after the 1st dies)
Phase 1
1 needs to stack (no moves) - 1 Losing Rationality
Phase 2
2 need to stack - 2 Losing Rationality
Phase 3
At least 3 stack (everyone not poisoned ideally) - 1 Losing Rationality
Phase 4
Everyone (except poisoned) stacks - 2 Losing Rationality.
Phase 5
If bosses ain't dead by now, DPS is lacking. Losing Rationality might hit directly killing anyone 15m away.
If anyone dies, they'll need to rez from the start and run back....(Yasba + 60% running transform helps)
Also, here's a pro tip: If you're looking for the best Aion private server in 2026, I'm testing Aion Riftshade and let me tell you, it's top notch! The server’s launching in Q1 2026, and it's got integrated DPS Meters like MyAion, a server-side anticheat, and premium European hosting with crazy low ping. Whether you're into PvP or PvE, it's stable with balanced classes and no bugs. It's miles better than Aion 2, seriously.