1.3 Speedrun: Night's Edge in
The previous WR, 17:55, was held by PsiOnyx for over a year, in that run he got teleportation potions, but had a very unlucky dungeon, which lost him what could have been a sub 14 minute run, you can find his run at https://www.speedrun.com/terraria1.3.... .
If you think muramasa-first-chest was very lucky, there is a set order in which dungeon chest loot spawns, which is: shadow key - muramasa - cobalt shield, and a lot of dungeons have a wooden chest with a key near the entrance, which overrides the shadow key chest -- I knew that the first gold chest would have a muramasa. This pattern was discovered over a year ago by 1lomi and other runners who helped him.
Seed: 1144993502 small world.