...
... but you know he'd be making death saves
for a few rounds too, so then there's the Athletics
checks to swim
inside the Bag Of Holding, and
the Endurance checks to hold his breath.
"Which Way Is Up" is probably a Wisdom check.
I.d.-ing the Bag is probably a Know-Arcana check,
or maybe he just knows that it is a Bag.
Anyway, this sounds like a: Poisoned + Death Saves + Bagged + Drowning skill challenge.
His partymates should have woken up after the surprise round.
Surprise:
Dude1 hands dude2 poisoned drink
Dude2 drinks poison, takes damage
Round 1:
Dude2 takes damage, very Very quickly fails all the skill challenge checks
Dude1 hopes nobody heard nothing, teleports (!) dude2 into the bag, minor action throws bag in water
Eleanor Gecks wakes up prone ... (which she's rather happy about, for entirely different reasons)
... and starts YELLING at everybody, cause she hates happiness regardless of it's form:
"WHERE ARE MY TATTOO MARKERS ?? !!"
rest of party free action responds with: I know nothing variants
She suc-ceeds (oh that's so shadar-kai) her Perception check that not enough people responded
free action yells at dude2: "YOU DIDN'T RESPOND YOU WORM !!"
Dude2 doesn't respond again because he's underwater
Dude1 says: "I'll respond for him, if you'll do that little shadar-kai trick
again ?!"
Round 2:
Dude1 says can we all go back to sleep now, high Bluff check roll
Gecks says oh no you don't Paladin, failing Sense Motive check
... standard action Trip on dude1, minor action starts grapple
Dude1 is now prone+grappled, having voluntarily lowered his AC and Will, but not his Fortitude.
Rest of Party free action reaches for their ear plugs, forgetting about Dude2.
OK I think I've talked myself into it.