First, I'm aware there was a recent thread about this that was closed by mods. I'm posting because I found that thread to be a somewhat frustrating experience while looking for a rules clarification / discussion on this issue. So what I want to do here is summarize the useful parts of that discussion and re-open it--hopefully without the bickering that lead to the original post being closed.
First, the issue:
By RAW, it seems like a player can long rest, cast Hex on any creature (say, a small mammal, leading to the character carrying around a "bag of rats") using a 3rd level spell slot or higher, and then immediately short rest while maintaining concentration to regain the spell slot. Now the character is concentrating on Hex with 7 hours (or 23 hours for 5th level slots and above) of spell duration left, but has full spell slots. (A separate but related issue is whether a fiend patron warlock would also gain temporary hit point from Dark One's blessing).
This question in the earlier thread seems to have elicited three main types of reaction:
1) You can't maintain concentration over a short rest.
2) This is gaming the system and should not be tolerated.
3) This is fine.
I'll try to summarize each of these in view of launching a renewed discussion.
1) You can't maintain concentration over a short rest.
There was some discussion as to whether the correct question is "can you concentrate while short resting?" or "can you short rest while concentrating?". Both are separate questions.
a) The rules seem clear that you can concentrate while casting other spells, or attacking, or running full speed until exhausted, or any number of things more challenging, mentally taxing, or exhausting than resting. And Mike Mearls has tweeted in support of this position, although it was pointed out that he does not issue rules clarifications, only opinions. Still, there's certainly no indication in the rules that short resting ends concentration.
b) Whether you can gain the benefits of a short rest while concentrating on a spell is arguably less clear. However, the simple fact that Hex (and Hunter's Mark) has up to a 24 hour duration with concentration suggests that RAI you can. This comes down to a question of whether concentrating on a spell is "... more strenuous than eating, drinking, reading, and tending to wounds." The problem is that the description of concentration doesn't address this. To my mind, the fact that you can cast another spell or run a marathon or (maybe) fall into lava without breaking concentration suggests that it's not all that strenuous. But I wouldn't be overly unhappy with a DM who ruled that you can't short rest while concentrating--although I think any DM doing so should be aware that they're probably weakening Warlocks and Rangers somewhat more than was intended. Otherwise, why bother with the long duration on Hex and Hunter's Mark? It seems fairly clear they're intended to last longer through a short rest, although certainly the game could've been clearer on that point.
2) This is gaming the system and should not be tolerated.
Honestly, as a player playing a Warlock who realized (as far as I understood RAW) that this mechanic was possible, this was my first reaction. I thought, "wait, so I would benefit from carrying a bag of rats around and murdering one every morning? That's... that can't be right."
But after thinking about it a while, I came to something closer to the view of one of the posts on the first page of that prior thread that got subsequently ignored: "I don't know, torturing rats seems pretty well in line with the attitude of many patrons...". Seriously. I have a fiend patron. I get temporary hit points for killing things, and if I kill something I hexed I can hex something else. And if I rest for an hour or so I can cast all my spells again. My character knows all these things, and can put it together as well as I, the player, can. Do we even know for certain that this is not intended?
Certainly this wouldn't be acceptable behavior for most people. But most people aren't adventurers who have made a pact with some otherworldly creature, which has then granted them powers. Power which, unless your answer to item #1 is no, are helped slightly by murdering something--anything!--and then taking a break afterwards. What's wrong with a small sacrifice...? Certainly this wouldn't be acceptable for an LG character, or arguably maybe even any G character. If I were DMing a G character doing this I'd want to have a talk with them about the ethics of their behavior, and what it might mean for their alignment long term. But for most other characters this is probably entirely reasonable behavior, given that they live in a world where this clearly benefits them, and they're no stranger to killing things.
With that said, if you object to the "bag of rats" (which, let's be honest, is basically understandable--it's somewhat obnoxious to manage and is pretty weird behavior, even if "my patron likes it" is a fully rationale in-game reason for doing it), you have two basic options for responding that I can see:
First, you can rule "no, you can't do that." That's fine, but your player will probably want to know, mechanically, why (note that you're entitled to say "because I think it's cheesy and makes the game less fun," or something to that effect). Other than saying that the answer to #1 above is "no", which has much broader implications and really does specifically nerf warlocks, the main option here seems to be to say that short resting after a long rest does not result in any additional benefits. The counter-argument here is that the end of the long rest results in concrete benefits, which the character has received, and then the character goes and does something else, rests for an hour, and gains the benefit a short rest. You can rule how you want here as always, but it's hard to see how "taking away" the short rest from players here makes very much sense either RAW or RAI. If you do, there's a real sense in which you're incentivizing your players to punch each other in the face once or twice after long resting in order to justify short resting. Pact magic slots (and ki points, superiority die, etc.) come back after an hour or so of light activity. Period.
But there's still another option below that doesn't result in the bag of rats:
3) This is fine.
There's too flavors of this answer.
a) DM rules that hex does not require a target, allowing the player to cast and concentrate on it and later use a bonus action to select a target, rather than selecting a target on the initial casting and then reducing that target to 0 HP. Apparently Mike Merls has also suggested that hex does need a target, so if you're going with his interpretations of the rules then you might stay away from this one. This ruling has the nice feature of not nudging warlock players towards murdering small animals on the daily, while also not leaving them (from 5th level and above) with 1 fewer spell slot in their first encounter of the day than they will have in the rest of their encounters (that follow a short rest), just because of a pretty quirky combination of game mechanics.
b) It just works as described. As far as I can tell this is RAW. It's definitely pretty messed up behavior, but players do all kinds of messed up things. There are literal necromancy spells for crying out loud. Those encourage players to straight up murder villagers if they can't find another source of corpses. I certainly hope no DM would say, "you can't do that" just because it's bad behavior in the service of game mechanics (for characters, real-world benefits!), but obviously if they weren't of an evil alignment I would hope the DM would say, "you do what now?" Honestly, although the rules on this issue could certainly have been written more clearly, I'm increasingly of the view that seeing this mechanic as against RAI requires believing that warlocks were not play tested past level 5. Because as soon as you get that 8 hour duration on hex as a player, you wonder "can I concentrate through a short rest?" And then when you figure out that answer (see #1 above), the first time you're in the first encounter of the day and you cast hex, you're thinking "wait so if I'd killed something before now I'd have another spell slot?" It makes you think about opportunities to kill things. It makes you think about killing small, harmless creatures ritualistically on a daily basis in service of your pact magic. And I just don't think that's at all thematically problematic for a warlock. I think warlocks, as they gain power, should probably be thinking about doing things exactly like that.
First, the issue:
By RAW, it seems like a player can long rest, cast Hex on any creature (say, a small mammal, leading to the character carrying around a "bag of rats") using a 3rd level spell slot or higher, and then immediately short rest while maintaining concentration to regain the spell slot. Now the character is concentrating on Hex with 7 hours (or 23 hours for 5th level slots and above) of spell duration left, but has full spell slots. (A separate but related issue is whether a fiend patron warlock would also gain temporary hit point from Dark One's blessing).
This question in the earlier thread seems to have elicited three main types of reaction:
1) You can't maintain concentration over a short rest.
2) This is gaming the system and should not be tolerated.
3) This is fine.
I'll try to summarize each of these in view of launching a renewed discussion.
1) You can't maintain concentration over a short rest.
There was some discussion as to whether the correct question is "can you concentrate while short resting?" or "can you short rest while concentrating?". Both are separate questions.
a) The rules seem clear that you can concentrate while casting other spells, or attacking, or running full speed until exhausted, or any number of things more challenging, mentally taxing, or exhausting than resting. And Mike Mearls has tweeted in support of this position, although it was pointed out that he does not issue rules clarifications, only opinions. Still, there's certainly no indication in the rules that short resting ends concentration.
b) Whether you can gain the benefits of a short rest while concentrating on a spell is arguably less clear. However, the simple fact that Hex (and Hunter's Mark) has up to a 24 hour duration with concentration suggests that RAI you can. This comes down to a question of whether concentrating on a spell is "... more strenuous than eating, drinking, reading, and tending to wounds." The problem is that the description of concentration doesn't address this. To my mind, the fact that you can cast another spell or run a marathon or (maybe) fall into lava without breaking concentration suggests that it's not all that strenuous. But I wouldn't be overly unhappy with a DM who ruled that you can't short rest while concentrating--although I think any DM doing so should be aware that they're probably weakening Warlocks and Rangers somewhat more than was intended. Otherwise, why bother with the long duration on Hex and Hunter's Mark? It seems fairly clear they're intended to last longer through a short rest, although certainly the game could've been clearer on that point.
2) This is gaming the system and should not be tolerated.
Honestly, as a player playing a Warlock who realized (as far as I understood RAW) that this mechanic was possible, this was my first reaction. I thought, "wait, so I would benefit from carrying a bag of rats around and murdering one every morning? That's... that can't be right."
But after thinking about it a while, I came to something closer to the view of one of the posts on the first page of that prior thread that got subsequently ignored: "I don't know, torturing rats seems pretty well in line with the attitude of many patrons...". Seriously. I have a fiend patron. I get temporary hit points for killing things, and if I kill something I hexed I can hex something else. And if I rest for an hour or so I can cast all my spells again. My character knows all these things, and can put it together as well as I, the player, can. Do we even know for certain that this is not intended?
Certainly this wouldn't be acceptable behavior for most people. But most people aren't adventurers who have made a pact with some otherworldly creature, which has then granted them powers. Power which, unless your answer to item #1 is no, are helped slightly by murdering something--anything!--and then taking a break afterwards. What's wrong with a small sacrifice...? Certainly this wouldn't be acceptable for an LG character, or arguably maybe even any G character. If I were DMing a G character doing this I'd want to have a talk with them about the ethics of their behavior, and what it might mean for their alignment long term. But for most other characters this is probably entirely reasonable behavior, given that they live in a world where this clearly benefits them, and they're no stranger to killing things.
With that said, if you object to the "bag of rats" (which, let's be honest, is basically understandable--it's somewhat obnoxious to manage and is pretty weird behavior, even if "my patron likes it" is a fully rationale in-game reason for doing it), you have two basic options for responding that I can see:
First, you can rule "no, you can't do that." That's fine, but your player will probably want to know, mechanically, why (note that you're entitled to say "because I think it's cheesy and makes the game less fun," or something to that effect). Other than saying that the answer to #1 above is "no", which has much broader implications and really does specifically nerf warlocks, the main option here seems to be to say that short resting after a long rest does not result in any additional benefits. The counter-argument here is that the end of the long rest results in concrete benefits, which the character has received, and then the character goes and does something else, rests for an hour, and gains the benefit a short rest. You can rule how you want here as always, but it's hard to see how "taking away" the short rest from players here makes very much sense either RAW or RAI. If you do, there's a real sense in which you're incentivizing your players to punch each other in the face once or twice after long resting in order to justify short resting. Pact magic slots (and ki points, superiority die, etc.) come back after an hour or so of light activity. Period.
But there's still another option below that doesn't result in the bag of rats:
3) This is fine.
There's too flavors of this answer.
a) DM rules that hex does not require a target, allowing the player to cast and concentrate on it and later use a bonus action to select a target, rather than selecting a target on the initial casting and then reducing that target to 0 HP. Apparently Mike Merls has also suggested that hex does need a target, so if you're going with his interpretations of the rules then you might stay away from this one. This ruling has the nice feature of not nudging warlock players towards murdering small animals on the daily, while also not leaving them (from 5th level and above) with 1 fewer spell slot in their first encounter of the day than they will have in the rest of their encounters (that follow a short rest), just because of a pretty quirky combination of game mechanics.
b) It just works as described. As far as I can tell this is RAW. It's definitely pretty messed up behavior, but players do all kinds of messed up things. There are literal necromancy spells for crying out loud. Those encourage players to straight up murder villagers if they can't find another source of corpses. I certainly hope no DM would say, "you can't do that" just because it's bad behavior in the service of game mechanics (for characters, real-world benefits!), but obviously if they weren't of an evil alignment I would hope the DM would say, "you do what now?" Honestly, although the rules on this issue could certainly have been written more clearly, I'm increasingly of the view that seeing this mechanic as against RAI requires believing that warlocks were not play tested past level 5. Because as soon as you get that 8 hour duration on hex as a player, you wonder "can I concentrate through a short rest?" And then when you figure out that answer (see #1 above), the first time you're in the first encounter of the day and you cast hex, you're thinking "wait so if I'd killed something before now I'd have another spell slot?" It makes you think about opportunities to kill things. It makes you think about killing small, harmless creatures ritualistically on a daily basis in service of your pact magic. And I just don't think that's at all thematically problematic for a warlock. I think warlocks, as they gain power, should probably be thinking about doing things exactly like that.
