Shotgun King: The Final Checkmate

First of all, turn on speedrun mode from the Options menu, so you have the timer in the bottom right corner. This will tick up on your turn, as well as on card selection between floors.

Victoria is your best bet, as you basically have 10 seconds per floor. You want to make a beeline for the king as quickly as you can without putting yourself in harm's way. I used 3 shields as a precaution, since I'd be in constant motion, and not checking to see if I was in danger before moving or shooting.

Obviously, this clip is only useful to show my stats (11 firepower, range 6-8, arc 57°). Your build will inevitably be different from mine, but I would recommend Black Mist anytime you see it, as well as anything that increases firepower. In terms of things to avoid, Theocracy will likely cause each floor to take longer, especially if you have multiple bishops. Likewise, avoid selecting cards that will give the white king extra HP.

Most importantly, don't give up. My best run was 2:04 for hours until I got this 1:35.91 out of nowhere. Just luck of the build.