UPDATE: Here are some ways to improve this build, thanks to viewer suggestions:
Choose feat spell focus (conjuration) to unlock Augment Summoning and Superior Summoning that boosts all summons beside Undead ones
Get CHA up to 12 or 14 to reap benefits from Lich Mythic path if you want to go for that one
Cruoromancer Wizard sublass is Necromancy focused and it can be truly awesome as summoner with all sorts of debuffing and offensive spells.
This is one version of necromancer summoner that i particularly like.
1:11 Leveling Process (Spreadsheet included)
3:31 Mythic abilities and Feats
5:32 How to play
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Pathfinder wrath of the righteous necromancer build