An issue has come up in during play regarding the cards(chaos cultists tokens, Corsair Trading Port, etc) that allow a player to reduce a unit's deployment cost by x amount.

For example, my opponent plays Promise Of Glory, putting two cultist tokens in play at his HQ. He then wants to deploy a Vicious Bloodletter, which costs 5 resources. However, he only has 4. With the cultists being sacrificed, the Bloodletter will only cost 3. Is he able to start deployment with insufficient resources and then trigger the cultists' interrupt making the cost 3?

I ended up ruling that you cannot start the deployment with insufficient resources, as the interrupt must wait until that happens. This seemed sensible to me, as I view these types of effects as a "refund" on the deployment cost. However, since the wording is when as opposed to after deployment, I may not have made the correct decision.

The Cultist sacrifice will allow you to deploy VB.

Cultist says: "When you deploy a Daemon unit, sacrifice this unit to reduce its cost by 1."

You declare your intention to deploy VB, and the 6 step deployment process initiates. Before step 1 of that process commences its resolution, you can interrupt this whole deployment process with the Cultist (or as many Cultists as you want given each can interrupt once). The sacrifice of the cultist creates a lasting effect (the cost reduction by 1), which will eventually be resolved in step 3 (apply modifiers).

After all interrupts are done, you now enter step 1 of the deployment process and check that you will be able to deploy VB. With the cost reduction lasting effects now enabled, the answer is yes.

And technically, that's how it's legal!

Good question ... I think I'll write this up as a tutorial at cardgamedb to add to the central rules repository.

The 6-step process PBrennan mentions is on pp8-9 of the RRG. The 6 steps (which are followed for initiating abilities as well as deploying cards) are:

1. Check play restrictions

2. Determine costs

3. Apply modifiers

4. Pay costs

5. Choose targets (if applicable)

6. Deploy card/resolve ability

Then RRG goes on to say that if any of these steps create a triggering condition for an interrupt, that ability can be initiated when the triggering condition becomes true. So I'd argue PBrennan's timing just a little. I'd suggest that it's Step #1, when play restrictions are checked, that you determine that a Daemon unit is being deployed, so that's where it looks like the triggering condition for the Cultist is established, and that is where you could trigger the interrupt, according to the RRG. The exact place in the process is probably less important than the fact that you do get a chance to interrupt the deployment process with a Cultist before costs are checked against your resource pool, so 3 resources and 2 Cultists will still allow you to play a 5-cost Daemon without problems.

I think you just said the same thing I did, so I'm not sure what the timing discrepancy might be ...

In practice, I'm not sure there are any interrupts / reactions to steps 2 through 4 (eg an interrupt to step 3 would be "when you modify costs", but there aren't any interrupts like that), although there are interrupts to choosing targets in step 5 and actual resolution in step 6 (eg cancel effects).

I was reading your answer as saying the interrupt came before Step 1 of the process - essentially after the player says, "I'm going to deploy something," but before play restrictions are checked. My sense is that the interrupt happens DURING Step 1 (instead of before it) because you need to have checked the play restrictions in order to confirm the unit has the Daemon trait.

It's splitting hairs, though, because we both agree the Interrupt would take place before cost is determined, modified and paid, so there is no inherent requirement for a player to have the resources to pay full price in order to even get the opportunity to trigger the interrupt.

Ok, I see. But it's a known fact that you're deploying a Daemon unit ... when you initiated the deployment you state exactly what you're deploying. The Cultist interrupt (in this case) can then successfully trigger off that initiation because it knows what you're deploying.

Having said all that, it feels weird that you can simply say you're deploying something, do sacrifices, get benefit from those sacrifices from other card effects (eg "when a unit is sacrificed, gain this ...") and then resolve step 1 and say, oh, it's an illegal deployment, and then stop the deployment. So maybe it is interrupting step 3 after all, or maybe this sequence isn't quite right for these sets of effects (it was borrowed from Star Wars). Let me take this offline and confirm it all with Nate and I'll come back, plus post it at cardgamedb in a tutorial.

Thinking more on it, Step 1 only ever checks for play restrictions - is it the right phase or not, etc. The deployment process doesn't check whether you have the required resources until you get to step 4 anyway (and that's the point you abort the process if you can't pay, without paying anything). But again, I'll confirm.

Either way OP, the answer is yes you can deploy VB.

Thanks to both of you! For some reason, I looked very perfunctorily in the RRG and missed it all. Fortunately, I have been playing this effect equally for all cards that have it, so it's a consolation. It doesn't seem to have affected Chaos too much. Mono-Chaos is a bear to deal with.

Ok, after much discussion, I've posted a tutorial at cardgamedb providing a fleshed out understanding of how the Deployment/Ability Initiation process is going to be ruled to work (for those who love the technical side of things):

http://www.cardgamedb.com/forums/index.php?/topic/18063-abilities-and-deployments-tutorial-interrupt-and-reaction-interactions/