This came up today at our gaming session. I was sustaining a Wall of Fire with my minor actions. The enemy was out of sight and I readied an action to Thunderwave them into the Wall of Fire if they appeared between the wall and myself. My DM ruled that, if the readied action went off, I would be unable to sustain the Wall of Fire.
Her rationale went like this:
- You are sustaining the power on your turn at your initiative count
- If your readied action goes off, your initiative count changes to a later moment in the round.
- Therefore, the turn following your readied action going off, on your original initiative count, the power would need to be sustained, but couldn't be until the new initiative count. By the time your new initiative came up, it would be too late.
Her main argument was that I would be getting it sustained for free for part of a round between my old initiative count and the new one. Potentially, it could encompass an entire round (If I was first in the initiative count and become last in the order after triggering my action.)
It never actually came up because the conditions of the readied action were never met.
My argument is that I'm giving up time in the round where I have to wait to act and that that counters any extra time that it is sustained. I didn't find anything in the PHB that covered this scenario specifically, which made me think that my reading of the rules was more correct. Sustaining happens on your turn. Using a readied action moves your turn later in the round, but you still have the chance to spend those actions on your turn.
If I'm right, we'll probably wind up calling her ruling a house rule and I'd be fine with that.
Note: Delayed actions are different and are specifically covered on p288 of the PHB: "At the moment you delay, … sustainable effects end.
Best Answer
Your DM is wrong in your specific case. I'm not sure whether you're saying delaying doesn't end a sustain -- it does -- so I'll cover readying first, then sustaining.
Readying is covered on page 247 of the Rules Compendium and page 291 of the Player's Handbook. Your reading is correct. You would have to sustain before you spent your standard action to ready, but on the next round your initiative would move as per your understanding, and you'd sustain at the normal time. This is in fact "free" sustaining; however, it's enough of a fringe case so that it's never bugged me. On the other hand, I can see it as a house rule. As a GM, I'd just ask people not to be abusive if they started metagaming around it, though.
Delaying is covered on page 242 of the Rules Compendium and on page 288 of the Player's Handbook. When your initiative comes around, your start of turn effects happen no matter what, even if you delay. Your end of turn effects are split into two parts. Any beneficial effects end immediately when you delay, and anything you were sustaining ends immediately. So yeah, your turn is moved later in the round -- but you still lose your sustains, and you don't get that free sustain for a portion of the round.