7 days, 12 skills.
I didn't have time to optimize it, and I'm already late.
On day 6, I captured all the castles, and all that's left is to kill one computer hero with 6 Hydras. I was a little short on money and extra heroes, about 2600.
In any case, I only aimed for 12 skills, but where did the 15 come from? Did some hero just run around to all the skill-boosting locations and shrines, pick up an artifact, and manage to fight in the end? Well, then that's a first-place finish.)
Charity suffereth long, and is kind; charity envieth not; charity vaunteth not itself, is not puffed up,
Doth not behave itself unseemly, seeketh not her own, is not easily provoked, thinketh no evil;
Rejoiceth not in iniquity, but rejoiceth in the truth;
Beareth all things, believeth all things, hopeth all things, endureth all things. Charity never faileth...