The power of the 
Abyss Sanctum skips the eldest setting off a chain of consequences.
Summary
Event: 
Zudaeshi’s Mother is skipped by the Sanctum magic when it comes time to choose a new 
Sanctum Master for the Abyss Sanctum
Mechanism: The Sanctum chooses its Master through a sacred, semi-sentient magical process no one fully controls
Expectation: Zudaeshi’s Mother, the eldest heir, was assumed to inherit
Outcome: The magic instead chooses Mulsae’s Grandfather
Speculation: The Water Sanctum rejected her for failing to embody its essential duality — life and death, stillness and motion, creation and destruction. She leaned too far into cruelty, unable to honor the sustaining side of Water
Consequences
1. Zudaeshi’s Mother defects to 
Archipelago of Shinra
Believes the Sanctum betrayed her
Marries into Shinra’s military caste
Raises Zudaeshi in a culture of conquest and slavery
Seeds intergenerational resentment
2. Archipelago of Shinra - 
Mountain Sanctum alliance
Her old allies (Garrick’s family) reestablish contact (Zudaeshi’s Mother and Garrick’s Father? Grandfather? Were lovers. But it's taboo to cross sanctum bloodlines)
They want to repair her legacy by merging bloodlines. Reject the taboo, make a powerful merged Sanctum.
3. Plot to reclaim the Abyss Sanctum
Hope: the Sanctum will switch to Zudaeshi’s bloodline
Secondary Consequences
Childhood friends; conflicted loyalty
Mulsae tells his father, hoping for diplomacy
2. Mulsae’s Father attacks first
3. Garrick retaliates
Joins Garrick’s Father in wiping out Mulsae’s family
4. Final Duel of the Sanctum Masters
The two patriarchs clash
Tertiary Consequences
Their friendship is shattered by mutual blame and guilt
Ongoing Ripple Effects
The war with Archipelago of Shinra is fueled by a feud whose origin no one living fully understands