Seems to me a thieves guild wouldn't want lethal traps (dead adventurers bring too much attention), they'd want a trap and release, probably with erased memories or into a situation that puts their veracity/ reliability in doubt, so that any attempts to reveal the location of the thieves to authorities would be ruined.

Closer in, for instance, might be traps designed to permanently alter intellect/ ability (drop intelligence points by causing brain damage that takes a serious healer to fix), or inflicting synesthesia (mixing up senses to where you hear color and smell sound, etc), or dysarthia (garbled/ slurred speech caused by muscle paralysis/ damage, they'd appear to be drunk).

And if any of the adventurers would be a good fit, try recruiting them ("you made it all the way here, that's incredible, we're looking for people Just Like You. You can go into dungeons and bring back loot for the guild, and in return you get Benefits XYZ...", and maybe the new recruits take a turn monitoring these traps for other adventurers now and again, which could be fun for the GM and also awkward as heck for the players...)

Yes. I'm very mean. Comes from being a writer.