1. Logistics
2. Find Path
3. Drain Life
4. Stone Skin
5. Tactics
6. Affinity with Magic
7. Drain Life (general)
8. Agony
9. Agony (general)
10. Archery
11. Dark Magic 1
12. Dark Magic 2 (+first damage bonus on the Path of Blood)
13, 14. -
15. Dark Elementals; Stop Time; Terror
16. Education (because after level 15, experience is gained slowly, and there's plenty of it before the 3rd mission in the campaign)
17. Stone Skin (general)
18. Dark Magic 3
19. Meditation
20. Explosion
21, 22, 23. Guardian of Secrets 1-3
24, 25, 26. Primal Magic
27. Mana Drain
28. Weakness
29. Weakness (general)
30. Giant Killer That's about it... I'll write a follow-up after completing the campaign to see how it works out. If it's good, I'll only play duels with this build... And one more question: can the Explosion spell be regenerated at all, either for undead or living creatures?