An Analysis of Soul Evolution in BoH

After doing a data-dive into the game files, I've come to some conclusions about the process of evolving your Soul Elements in Book of Hours.

First, there are four possible levels of Soul Element. To go up a level takes two Soul Elements of the same level. A bit of math shows that to evolve a Soul Element to the highest level will require eight Soul Elements of the first level, and you'll need seven Skills that can validly evolve that Soul Element. (As an aside, to get all of your Soul Elements to Level 4 takes a total of 8 \* 9 = 72 level 1 Soul Elements, and there are 73 skills...)

There are **four Skills which have** **no valid evolutions**, and 24 Skills with only one.

The four skills with no option to Evolve:

* Fucine: This skill is 2 Heart, 1 Knock at level 1 and can be assigned to Hushery to gain Trist, or Ithastry to gain Wist. However, no Hushery or Ithastry workstation accepts Heart or Knock. * Hill & Hollow: This skill is 2 Moon, 1 Scale at level 1 and can be assigned to Preservation for Health, or Birdsong for Chor. There are no Preservation workstations that take Moon or Scale; and while the Sunset Harp takes Moon, it doesn't take Grail or Heart. * Preliminal Meter: This skill starts as Knock 2, Rose 1 and can be assigned to Illumination for Phost, or to Ithastry for Wist. No Illumination or Ithastry workstation accepts Knock or Rose. EDIT: It has been pointed out that the Watchman Shine does take Rose, and so this skill can be used for Phost. * The Great Signs & the Great Scars: Starts as 2 Grail, 1 Knock and can be assigned to Hushery for Trist, or Horomachistry for Fet. No Hushery Workstation takes Grail or Knock; and the one Horomachistry Workstation that can accept the skill (the Great Clock) can't take Fet.

The 24 Skills with only one evolutionary path:

* Applebright Euphonies: The Bosk (Ereb) * Desires & Dissolutions: The Bosk (Ereb) * Disciplines of the Scar: Illumination (Phost) * Door & Wall: Nyctodromy (Shapt) * Drums & Dances: The Bosk (Health) * Edicts Inviolable: Preservation (Chor) * Horns & Ivories: Skolekosophy (Shapt) * Inks of Containment: Horomachistry (Mettle) * Inks of Power: Hushery (Trist) * Meniscate Reflections: Illumination (Phost) * Orchids & Narcotics: The Bosk (Ereb) * Path & Pilgrim: Nyctodromy * Rites of the Roots: Preservation (Health) * Sabazine: Horomachistry (Fet) * Sand Stories: Birdsong (Trist) * Serpents & Venoms: Hushery (Trist) * Sickle & Eclipse: Nyctodromy (Shapt) * Sky Stories: Horomachistry (Fet) * Solutions & Separations: Skolekosophy (Shapt) * Stone Stories: Preservation (Chor) * Transformations & Liberations: Ithastry (Phost) * Vak: Nyctodromy (Fet) * Weaving & Knotworking: The Bosk (Health)