Found a list, but it's in German, so here you go. The number is how many star stones you need:
1) Homestead with Observatorium
2) Hall of Heroes: Storage place for unused party members, lets you hire henchmen.
3) Inner Chamber: Storage for items, change your appearance.
4), 6), 8) 11) Elemental rooms: One for each element, lets you buy skillbooks for elemental magic and one other type (for example the Fire room sells Fire Magic and Man at Arms)
5) Hall of Secrets: lets you buy secrets
7) Hall of Darkness: lets you reskill your main heroes
9) Armory: lets you forge your equipment in the Homestead
10) Shop: sells items
12) Chapel: buy big Potions of Resistance
Never) Forbidden Zone: Awesome cool place of greatness. No Source Hunters allowed.
Last edited by Daris; 03/08/14 12:16 PM. Reason: found some info