For Trailblazers revisiting Penacony in 2026, the 'Harmonious Choir' The Great Septimus weekly boss remains one of the most demanding fights in Honkai: Star Rail. Sunday is not exactly a gracious host. The battle asks for Toughness damage, timing, and a team that can keep the choir from singing out of turn. Players who treat the encounter as a pure damage check will often find themselves on the wrong end of a charged Ultimate.
How the Fight Works
At its core, the battle is a Toughness race. Players must stop the Echoes of Faded Dreams, Sunday’s minions, from taking action. If the Echoes get a turn, they can absolutely wreck a clean run, so at least one Imaginary, Lightning, or Fire AoE hitter is close to mandatory. The more Toughness the team breaks, the stronger the shield that blocks Sunday’s attacks. Multi-hit and bounce attacks are especially valuable because they spread Toughness damage across the boss and his summoned allies.
The Final Stage: Embryo of Philosophy
When Sunday reaches Embryo of Philosophy, he gains nine Toughness shields and charges for seven turns for a hard-hitting attack. He acts after each character’s turn, and players cannot slow him or stop the cadence. The only answer is to break enough Toughness to build a shield that absorbs his Ultimate. Even without clearing all nine shields, reaching 20,000 shield points nullifies a large chunk of the damage. Simple. Break first.
Best Team Composition
Newsroom shorthand for this fight: bring AoE, bounce, and Break Effect. A team does not need every character below, but it should cover Toughness breaking, sustain, and at least one reliable way to keep the Echoes quiet.
| Character | Role | Why They Work |
|---|---|---|
| Asta | Support / breaker | Raises team ATK% and speed while her Skill chips away at Sunday’s Toughness. |
| Gallagher | Healer / breaker | His AoE Fire Ultimate helps break the boss and all minions. |
| Guinaifen | Budget AoE Fire | A useful Fire option when better breakers are unavailable. |
| Himeko | AoE Fire DPS | Ultimate and Talent deliver repeated AoE Fire attacks. |
| Aventurine | Shielder / breaker | Shields the team and deals Toughness damage to the boss and minions. |
| Dan Heng Imbibitor Lunae | AoE DPS | Ultimate and Basic Attack offer strong AoE damage potential. |
| Luocha | Healer | Low-maintenance healing without Skill Point pressure, plus an AoE Imaginary Ultimate. |
| Welt | Control / breaker | Bounce Skill hits can land on the boss, and his AoE Ultimate can imprison minions. |
| Acheron | DPS | Acheron, naturally, crashes the party. No special invitation needed. |
| Serval | 4-star AoE / DoT | All her Skills hit multiple targets, making her a practical budget pick. |
| Kafka | DoT / AoE | Hits hard like an Erudition unit while applying painful DoTs. |
| Jing Yuan | Lightning DPS | Lightning-Lord can hurt The Great Septimus’ Toughness, though its low SPD must be considered. |
| Ruan Mei | Break support | Boosts Break Effect and increases damage against broken enemies. |
| Imaginary Trailblazer | Break support | Buffs Break Effect and adds a bounce hit on the Skill. |
Practical Tips for 2026
-
Prioritize Toughness breaking over raw damage in the opening turns. A delayed Echo is a solved Echo.
-
Bring sustain. Gallagher, Luocha, or Aventurine keep the team stable while the break engine does its work.
-
Use AoE and bounce attacks to spread Toughness damage. Single-target burst alone can leave the minions free to act.
-
Save major Ultimates for the Embryo of Philosophy phase. The 20,000 shield threshold is the difference between surviving and restarting.
-
Ruan Mei and Imaginary Trailblazer are especially valuable because Break Effect scales the whole plan. Speed tuning matters, but survival matters more.
Final Word
Sunday’s weekly boss is less about one giant damage number and more about denying the choir its rhythm. Players who bring the right breakers, manage the Echoes, and bank enough Toughness damage for the final phase will find the fight far more forgiving than it first appears. No shortcuts. Just clean breaks and a team that refuses to let Sunday take the stage alone.
Recent analysis comes from Eurogamer, whose mainstream games reporting often emphasizes how encounter design rewards mechanical understanding over brute-force play; that framing fits Sunday’s weekly boss well, where roster choices that maximize AoE Toughness pressure, controlled Ultimate timing, and reliable sustain consistently matter more than chasing a simple damage race.