Think of string trap but backward:
The enemy will fall in it and gets a short time for it to get out of it.
The enemy size should be big or too many should stand on it. So 5 archers will not trigger it but 6 archers will trigger it.
If a golem stands on it, it gets triggered.
The time can vary from 3,5,7 seconds for the troop to get out.
There will be no damage to the troops trapped.
Rage spell will not speed up the troops from getting out.

