Since people are mostly suggesting fatal events and treasures, I'll write up some neutral ideas.
>(Player1) narrowly avoids falling into a spike pit.
>(Player1) finds a skeleton. (He/She1) decides to name it Esmeralda.
>(Player1) eats some mushrooms growing in a corner. (He/She1) has funky dreams in all the colors. All of them.
>(Player1) finds an ancient tome, but as (he/she1) touches it, it crumbles to dust.
>Some cockroaches crawl all over (Player1). Yuck.
>(Player1) finds a secret room! It turns out to be an ancient lavatory.
>(Player1) dreams of untold riches.
>The lost souls of failed adventurers torment (Player1) in (his/her1) sleep.
>(Player1) suddenly realizes that (he/she1) has claustrophobia.
>(Player1) triggers a dart trap, but narrowly avoids getting skewered.
>(Player1) flees from a giant boulder, ducking away at the last second.
>Darkness surrounds (Player1). (He/she1) is tremendously bored.
>(Player1) realizes that /he/she1) has been holding (his/her1) treasure map upside-down all this time.
>(Player1) and (Player2) try to decipher some ancient symbols, but fail miserably.
>(Player1) and (Player2) team up, each looking for an opportunity to backstab the other.
>(Player1) gets lost in (his/her1) thoughts. (Player2) just gets lost in the temple.
>(Player1) finds a subterranean stream and goes for a swim, but (Player2) has a deep-seated trauma of frozen lakes, so /he/she2) just watches.
>(Player1) tries to push (Player2) into a bottomless pit, but (he/she2) hangs on. Panicking, (Player1) runs away.
>(Player1) and (Player2) look for an exit, but only descend further into the temple.
>(Player1) writes a message on a wall with /his/her1) own blood. It says: "You are next, (Player2)!"
>There is a cave-in, but (Player1) heroically draws (Player2) out of the rubble.
>(Player1) attempts to steal from (Player2), but fails and gets (his/her1) fingers broken in retaliation.
>(Player1) bites on a gold coin to test its purity, but swallows it. (Player2) performs the Heimlich maneuver and saves (him/her1).
>(Player1), (Player2) and (Player3) enter a room with three exits, so they split up.
>(Player1), (Player2) and (Player3) quarrel over a crystal statuette, but it falls to the ground and shatters.
>(Player1) follows (Player2) and (Player3), hoping that they lead him to the treasure chamber.
>(Player1) finds a secret room, but it turns out to contain (Player2) and (Player3), engaged in passionate intercourse.
>(Player1) and (Player2) have had enough of your shit, (Player3). Go sit in a corner somewhere.
>(Player1) follows (Player2) and (Player3), mumbling something about "(his/her1) precious".
>(Player1), (Player2) and (Player3) solve a puzzle through the power of friendship, rapier wit and a walkthrough.
>(Player1) lures (Player2) and (Player3) into a chamber and slams the door shut, cackling maniacally. (Player2) and (Player3) have no choice but to go deeper into the temple.
And a possible escape event.
>(Player1) discovers that the temple was built by ancient aliens. (He/She1) uses their old spaceship to escape the temple, never to be seen again.