[Kobal2]

Vanilla or CBM ?

In vanilla, look no further than Tartarians. A D4 Witch King can summon them with just a Skull Staff, Skull Helm and a Ring of Sorcery (or the Black Book of Secrets). All you need is S3/E2 on your god to make the Ring (crystal coin and astral cap get you to S5). In that case, you will still need to heal the tartarians, and for that you'll need a pretender with either enough Nature to cast the Mother Oak then Gift of Health (mother oak necessary, else the guy who cast the Oak will just steal your GoH) or enough Nature and Astral to forge the Chalice. N5 recommended.

In CBM, Tarts were nerfed to Hell and back so they're hardly worth it anymore. I would look at Wendigos (W3D3 - your Witch Kings with a water pick can summon them with both Water boosters - need W2/3 on your god though, can't expect to get a W2 Witch King)

Demons from the blood magic school would also be an option in both vanilla and CBM, but in that case you'll either want Blood 3/Nature 2 or Blood 4 on your pretender, or need to empower a Blood 2 WK in blood once to make Blood boosters (armor of thorns with a thistle mace, put it on, then blood thorn & brazen vessel).
With an armor of thorns, blood thorn, skull face and brazen vessel a B2 Witch King can summon a Vamp Lord. Give *him* the boosters and he should be able to summon Heliophagi. Empower him in Fire once (with income rooted out by your rainbow pretender) and he can make a skull of fire, then summon the Arch Devils. Or there's always moar Vamp Lords I suppose.

Finally, the Gift of Reasoned Daughter of Typhon is always a laugh.