For every character besides the player, there is an action that will cause that character to wither right up and die.

"Cactus Will Outlive Us All"
Death Valley is a room. Luckless Luke and Dead-Eye Pete are men in the Valley. A cactus is in the Valley. Persuasion rule: persuasion succeeds.
A person has an action called death knell. The death knell of Luckless Luke is pulling the cactus. The death knell of Dead-Eye Pete is Luke trying dropping the cactus.
Before an actor doing something:
   repeat with the victim running through people in the location:
      let the DK be the death knell of the victim;
      if the DK is not waiting and the current action is the DK:
         say "It looks as if [the DK] was the death knell for [the victim], who looks startled, then nonexistent.";
         now the victim is nowhere.

If we leave it at that, then pulling the cactus will kill Luckless Luke but then say "Nothing obvious happens.", which seems like a bit of an anti-climax. So we add a special case response for that one:

After pulling the cactus when Luckless Luke was in the location:
   say "That's a real shame."
Test me with "get cactus / drop cactus / luke, get cactus / luke, drop cactus / pull cactus / look".
Test me with "get cactus / drop cactus / luke, get cactus / luke, drop cactus / pull cactus / look".
Death Valley
You can see Luckless Luke, Dead-Eye Pete and a cactus here.

>(Testing.)

>[1] get cactus
Taken.

>[2] drop cactus
Dropped.

>[3] luke, get cactus
Luckless Luke picks up the cactus.

>[4] luke, drop cactus
It looks as if Luckless Luke dropping the cactus was the death knell for Dead-Eye Pete, who looks startled, then nonexistent.

Luckless Luke puts down the cactus.

>[5] pull cactus
It looks as if pulling the cactus was the death knell for Luckless Luke, who looks startled, then nonexistent.

That's a real shame.

>[6] look
Death Valley
You can see a cactus here.