Dark Spell Factory at Town Hall 12: max level 6. At Town Hall 18 the cap is level 8. It unlocks at Town Hall 8. Max level per Town Hall: TH8 2, TH9 4, TH10 5, TH11 5, TH12 6, TH13 6, TH14 7, TH15 8, TH16 8, TH17 8, TH18 8.
Tap a Town Hall to open this item there. Dashed: not available at that Town Hall yet.