"Help a monster" levels - any example PWADs?

[finnw]

I have an idea for a level design and I assume something similar must have been done before and I am looking for examples to follow.

The player's job is to guide a monster to the exit. The rules would be:

* The monster must be kept alive, i.e. the player must not kill it, and if it gets into a fight with another monster the player must ensure that it wins.
* The monster is *not* friendly. It will attack the player just like every other monster does.
* If the monster dies, the player dies also (maybe instant death, or maybe it causes a horde or bosses to teleport in with insufficient ammo available to kill them.)
* The monster must reach a gate to allow the player to exit the level (maybe the player exits immediately or maybe a door opens for them.)

How this might be implemented in Vanilla Doom:

* The key monster would have to be a mancubus, and the level would have to be MAP07.
* The "monster exit" would be a type-125 or 126 linedef that would teleport the mancubus to a remote room where it would open a door (using a type-1 linedef) which would share a sector with the door between the player and the player exti.
* A "tag 666" sector would open if the mancubus died, releasing a horde of boss monsters to kill the player.
- All monsters except for the mancubus would have to be caged to prevent them reaching the gate (so demons would not be very effective in this level.)

Where might I find an existing PWAD that uses the same or a similar trick?

[Mithran Denizen]

The closest thing I can think of is that in a level or two of Mars Doom, you have to escort a friendly monster (with sprites to make it look like a girl) around, though I don't really recall how it worked, and I think it was pretty DeHackEd-heavy.