Tried getting these quests on a rogue with sneak, they don't give necro skullcap dialogue at indifferent, so the minimum is probably amiable faction. Same responses for all the skullcap dialogues on the whole quest chain. (quests : necromancer 1st rank --> 7th rank is what I checked)
[Mon Aug 08 12:55:27 2022] Master Xydoz regards you indifferently -- looks like he would wipe the floor with you! (Lvl: 70)
[Mon Aug 08 12:55:28 2022] You say, 'Hail, Master Xydoz'
[Mon Aug 08 12:55:28 2022] Master Xydoz says, 'When you have shown more devotion to the Brood of Kotiz, we can discuss such things.'
[Mon Aug 08 12:55:32 2022] You stop sneaking.
(Kos)
[Mon Aug 08 12:55:32 2022] You say, 'Hail, Master Xydoz'
[Mon Aug 08 12:55:33 2022] Master Xydoz says, 'You are a true simpleton to think you can speak to me. You are no ally to the Brood of Kotiz. Begone, before I make your blood boil!'