This was a very interesting run. I wanted to try out Wyrmlet, which I was not very familiar with. Its first stage is quite weak, I feel, but damn if it grows. I instinctively raised up its Int since its active ability works with this stat, and I'm SO happy I did that. I can not be sure, but if the abilities you can choose when it evolves are always the same, I feel that Int could be the best option. Magical Acceleration + Power Overflow is great. On top of that it's magical, so if you pair it up you obtain even more mana regen.
And here is the sacred mega combo I used in this run: BONE RING + CIRCLET OF ACUITY!!! Wyrmlet just continuously casted. Countinuously. And with 150+ Int and Power Overflow it just kept destroying everything.
I won even after messing up my route and missing a Shard to upgrade Karakai.
Final Boss Note: Humble feedback. I think the tentacle final boss is the easiest one of the three. The spiky dragon and Voss are quite scary sometimes, but I've never had much trouble against cthulu's brother. But maybe there are some builds that suffer against it and I'm missing them by luck, dunno.
Anyway, very interesting indeed, Wyrmlet. I thought it was weak, since the first runs I could not go very far with him, but now that I'm getting the hang of the game, I understand its power.