I thought it might be fun to post some encounters with alternate goals for the PCs and monsters here for discussion and reference. Here's a scene from a one-shot "delve-style" adventure I'm running this month called "Dogs of War."
T H E S I T C H
The gnolls have dug their trenches close to yours and have found a weak spot in your lines to exploit. They are about to send a raid over the top and through your lines to get into Fort Castle. Stop them or be one step closer to watching the fall of the last bastion of man.
O B J E C T I V E
Prevent the gnolls from moving off the left side of the map. If three or more gnolls manage to make it across, you fail and the scene ends. PCs start in the reserve trench on the left side of the map.
T E A M M O N S T E R
Braaag, a reskinned b'rohg (10th-level elite soldier)
2 infernal contraptions, reskinned constructs of some kind (8th-level standard artillery), RBA attacks 1 to 3 targets
15 gnoll claw fighters (6th-level minion skirmishers) that have an interrupt to avoid AoE
6 iron boot mines (6th-level minion traps) that you can lose a foot on
Monster Goals: Braaag sets about tearing up sections of the barbed wire so the gnoll minions can get through it. He and the gnolls know where all the iron boots are. The infernal contraptions sit in superior cover and fire on any enemies foolish enough to stick their heads up. Gnoll minions start in the reserve trench. On their turn, they move to the communication trench and to the front-line trench, prone and crawling if possible. If there are no gnolls in the reserve trench at the end of a combat round, five more gnolls are placed on the map in the reserve trench. When three such waves are filling the trenches, the gnolls go over the top and rush the PCs' lines trying to make it off the map.
With all that said, how do the PCs prevail? What encounters have you done that have alternate goals like this? Let's get a few posted and a discussion of ideas!