Voted for the leaders:
Forest - B&B. It would be interesting to see a dual leader.
Sword - Celia. Hedgehog is cool, but hmm... Unless Mars is a worthy competitor.
Rune - Oz. Let it be, the options aren't very interesting.
Dragon - PDK. There's not much to choose from... The new legendary seems good, but it doesn't really appeal to me; I was more considering Jervu, but I think there's already a similar type in the form of the dragoon.
Shadow - Alice. But here it's really difficult; I wanted to vote for Aisha, Ceres, and Ceridwen... In the end, I leaned towards Alice; it's hard to say why, maybe I just haven't seen her as much as the others, but her map is interesting.
Blood - Karabossa. The options aren't very good. Scarlet and Emerald are too similar to Exella. Spawn? Yorm? It would be funny if Blood was the first to get an outright ugly creature as a leader.
Haven - Taurus. A Taurus as a leader? I'd take that!
Portal - Orkis. The optimal option; the others are just neutral-skeptical.
Meanwhile, I finally managed to do this in ranked.
This is what you do when normal legendaries don't drop.
The opponent was missing just one (!) artifact to completely clear Magma. Although, judging by the fact that he threw a bunch of stuff on the next turn and conceded, he didn't have Magma in his hand, so I got lucky...
Of course, you only go into ranked with this when you're in the mood to "let's give people the joy of victory!" It's good to be at zero master points; you can run meme decks to victory