for the discussion, creation and advancement of the aforementioned character
I believe that covers it.
Mechanically or what do the rituals look like?
I'm thinking it is "calling through the grave door"
basic score is stress die+presence+summoning+aura+lore with whatever lore will best represent knowledge of the being to be summoned...
the magic (obviously) specializes in calling forth the spirits of the dead. It also will generate a penetration score and summon the spirit into a container- for those which had it their corpse is preferred for penetration. For spirits which have no body some form of vessel must be prepared by crafting- wood and pottery being common The vessel must incorporate an arcane connection, frequently the name or true name of the spirit.
From here it will be very similar to the Sahir tradition, except that 1/2 of (aesthetic quality-8) is added to the bargain roll for the aesthetics of the vessel if it is not their corpse.
an art
a corpse will automatically animate, but vessels generally must be enchanted to move if that is desired. An animate vessel allows the spirit to work as a lab assistant, whether it was Gifted in life or not.
It does require an arcane connection, locating an appropriate spirit can be done with an appropriate lore role (area lore, organization lore, religion, etc) depending on the type of spirit being sought. Also the "bargaining" need not use the bargaining ability- other forms of persuasion are acceptable substitutes (unless you happen to be dealing with Jinn).
sorry, no standard vis cost, except by type. So if you are summoning a daimon- bid vis cost, Jinn? standard vis cost. Aunt Becky? No vis cost.
The spirit can animate the corpse until it decides to leave, or the corpse is destroyed.
In terms of background for your tradition, I am linking this;
Norse Ghosts & the Afterlife - Ancient History Encyclopedia