Okay, after aborting my Mystera super-run, I got a run that was just begging for me to use ENDISWAL.
I found the ENDISWAL early in dungeon exploration, but I held off. Then I discovered the Binlor and Pactmaker's altars sitting side-by-side, as if fate itself was tempting me. The sole remaining altar was Earthmother, so it was that or nothing, but I held strong! I ended up winning Parched and Faithless, though I don't feel faithless really counted because I used sparkles to fuel a single use of the scholar's pact. Second boss was Iron Man, so I used no poison in fighting the bosses. I'm doing the writeup right now, should have it up in 15-20 minutes.