Stage 5 of the John Van Caneghem Tournament

Apparently, we had different Walkthroughs; I didn't encounter any difficult battles at all. That's why I'm not very sure that 10 days to capture the Tear is the limit; everything was completed with a large margin, and this very often means that the Walkthrough is not optimal.

Level 12 or day 12? Because there should be more of those elemental, phoenix, ghost, and other minor units.

Oh, yes. This is our purely Necromancer art; it would be a sin not to take it.

Yes, I made a mistake – it wasn't level 12, but day 12.

Well, I simply spent 7 days leveling up the hero to level 14, not going far from the city, only exploring the Dungeon. Which is definitely tactically incorrect. And then, on the 8th day, I launched a blitzkrieg from the city towards the Tear – by the end of the 10th day, I reached the excavation site.
Since the minimum result could still be only 12 days, I didn't worry too much about the order in which to level up the hero (first towards the Tear, and then further level up the hero's characteristics...like you did).

But still, your result is better – you reached the Tear too quickly!!!