So the ways to model a tranq dart (or other sleep-inducing effect) would involve one or more of the following:
Round 1: Block versus doing anything
Subsequent rounds: maneuvers to plant "Sleepy" aspects
Take-down: physical stress to take out the target, tagging previous "Sleepy" aspects
In the case of Tranq darts fired by gun-wielding mortal agents, and not sleep spells, would we assume the NPC can perform all three of these actions, or would we create a Stunt to reflect this particular tactical use of their Guns skill?
How I'd model a tranq gun is a weapon that acts like a block vs anything, essentially until they wake up, or a weapon that does enough damage to completely take out anyone of a certain amount of stress track, so that the toughest migration struggle to stay awake.
I prefer the take out effect. Why? Once hit, and affected, a target would geneeally be out for minutes at least, and more likely hours. That's a lot closer to being taken out than anything.
Hm; weapon 5, only normal living creatures. Or....
Well, the problem is DFRPG has rules for continuous damage for precisely two.sources: the venomous add-on for claws, and environmental sources. Nothing else causes ongoing damage.
This, to me, is a flaw. So, I've purchased Strands of Fate, and I plan to port over some of their rules, including continuous damage and persistent aspects.
Then a tranq dart could do continuous damage... for a limited number of rounds. Or, there.are.other possibilities, but I'll wait until I'm done reading the book.