I’m pretty sure it behaves just like hex. If the target dies, use your next available BA to move the mark. 

If they meant the next turn, they probably would have written next turn, not "a subsequent turn", so I would think you could wait a few turns, or even a few hours if it is still active

If you are a ranger with two shortswords and use dual weapon fighting, does "hit it with a weapon attack" mean I get to apply it twice for this attack action or only once per attack action?

What is its casting time

So, settle a debate between me and my DM:

I believe that using the word "subsequent" lets me carry this spell with me as long as the concentration remains. So if I have a battle, that battle ends, and another battle begins in another part of a dungeon a few minutes later, than as long as I hadn't broken concentration, I should be able to once again mark another target.

But he insists that these type spells are battle to battle, and that my character wouldn't maintain concentration on a spell once he believed a battle to be over. I maintained that as we're exploring a dungeon, I would never stop being ready for a fight.

Thoughts?

Quote from RadioGuyRob >>

So, settle a debate between me and my DM:

I believe that using the word "subsequent" lets me carry this spell with me as long as the concentration remains. So if I have a battle, that battle ends, and another battle begins in another part of a dungeon a few minutes later, than as long as I hadn't broken concentration, I should be able to once again mark another target.

But he insists that these type spells are battle to battle, and that my character wouldn't maintain concentration on a spell once he believed a battle to be over. I maintained that as we're exploring a dungeon, I would never stop being ready for a fight.

Thoughts?

 

 

Beyond 20

 

 

 

 

 

It kinda sounds like your DM is just asking for an excuse to make you burn spell slots. By RAW, combat ending is not a factor that can break concentration.

From Basic Rules, Spellcasting Duration (PHB, 203-204)

If a spell must be maintained with concentration, that fact appears in its Duration entry, and the spell specifies how long you can concentrate on it. You can end concentration at any time (no action required).

Normal activity, such as moving and attacking, doesn't interfere with concentration. The following factors can break concentration:

• Casting another spell that requires concentration. You lose concentration on a spell if you cast another spell that requires concentration. You can't concentrate on two spells at once.
• Taking damage. Whenever you take damage while you are concentrating on a spell, you must make a Constitution saving throw to maintain your concentration. The DC equals 10 or half the damage you take, whichever number is higher. If you take damage from multiple sources, such as an arrow and a dragon's breath, you make a separate saving throw for each source of damage.
• Being incapacitated or killed. You lose concentration on a spell if you are incapacitated or if you die.

The DM might also decide that certain environmental phenomena, such as a wave crashing over you while you're on a storm-tossed ship, require you to succeed on a DC 10 Constitution saving throw to maintain concentration on a spell.

Tl;dr: if nothing else is disrupting your concentration, the only thing that limits how long a spell can be held is the duration limit specified in the spell's description.

yes

Quote from RadioGuyRob >>

So, settle a debate between me and my DM:

I believe that using the word "subsequent" lets me carry this spell with me as long as the concentration remains. So if I have a battle, that battle ends, and another battle begins in another part of a dungeon a few minutes later, than as long as I hadn't broken concentration, I should be able to once again mark another target.

But he insists that these type spells are battle to battle, and that my character wouldn't maintain concentration on a spell once he believed a battle to be over. I maintained that as we're exploring a dungeon, I would never stop being ready for a fight.

Thoughts?

 

 

Beyond 20

 

 

 

 

 

 It would state "the next turn" if that were the intention. It even uses the very open "a" when describing which subsequent turn. If your DM really wants to burn your spell slots for no good reason, just shift it to a fly or something at the end of each fight and carry it around with you in a vial or something so you can easily get it ready when combat seems imminent or pop it open and stick your finger in on your first turn. Hell, don't want to risk wasting an action/BA? Find a way to stick the fly to the handle of the weapon so it dies when you draw the weapon. It's a pretty good spell, but it's not good enough to make that arbitrary limitation, especially when it uses your concentration (which does also prevent you from dropping it as a 5th level before a long rest unfortunately)... And if you're using the variant where it doesn't require concentration? It doesn't count against your spells known and can be cast without expending a spell slot probably a good 2-3 times at least per long rest...

Quote from Kazamaraz >>

Quote from JNevins234 >>

I get that the spell requires concentration so that you don't crazy stack bonuses.  But for the life of me, I can't figure out why on earth you would cast this as a higher level spell to increase the duration.  [...]

Sure, it's a first level spell and at 11th level I have 4 spell slots for these per day, so if you get debuffed halfway into an encounter, no big deal, cast it again.  But please don't insult my intelligence as tell me that you are going to be able to maintain concentration for a spell that gives you combat/damage related buffs for 8-24 hours!  So lame… again, in MY opinion.  I could be wrong.

The Class Variant Options in last year's Unearthed Arcana fixes this, Rangers get it for free, no spell slot, doesn't count against your prepared spells, and best of all, doesn't use concentration.

 Well, with Tasha's Cauldron release, the "hunter's mark" class variant (Favored Foe) is back to requiring concentration, so that doesn't help... and it's limited to the first time on each of your turns that you hit your favored enemy (marked target).... vs "whenever you hit" with Hunter's Mark.  They dropped the ball with this variant feature. Doesn't solve anything, except to save spell slots for those ranger players that always cast hunter's mark.

My idea: Revised Favored Foe... that simply modifies Hunter's Mark using the wording of the Fey Reinforcement feature (11th level, Fey Wanderer)...

"You know hunter's mark. It doesn’t count against the number of ranger spells you know, and you can cast it without [...] components. You can also cast it once without a spell slot, and you regain the ability to do so when you finish a long  rest [perhaps short rest?]

Whenever you start casting the spell, you can modify it so that it doesn’t require concentration. If you do so, the spell’s duration becomes 1 minute for that casting."

Note: Multiple casting wouldn't stack, as per the Combining Different Effects rule. 

Does this stack with the new Favored Foe feature in Tasha's?  If not, then Favored Foe seems really bad.

Both hunter's mark and favored foe require concentration, so they can't be active at the same time.

Does it cost another spell slot to move it to another target?

Quote from ColdLogic >>

I’m pretty sure it behaves just like hex. If the target dies, use your next available BA to move the mark. 

 Close.  It's a BA on any subsequent turn - so you couldn't kill a target and then move the hex/mark on the same turn but, if your target is already dead, you could move the hex/mark onto a new target and then attack it.

Quote from 2PlyMcSnippz >>

Does it cost another spell slot to move it to another target?

 

 If it did it would be stated in the spell.

A possible use for the extended time period would be a chase scenario. You've made it through the cannon fodder, and are facing the bbeg of this encounter or quest. You get him to 50% hp and he's like "***** this, I'm out!" You cast hunter's mark as he's fleeing but within range (one turn window to do so, i would think) and boom. He's easier to track down and finish the job before his or your next long rest. 

Do you have a link for the source I can't find this variant.

Quote from Kazamaraz >>

Quote from JNevins234 >>

I get that the spell requires concentration so that you don't crazy stack bonuses.  But for the life of me, I can't figure out why on earth you would cast this as a higher level spell to increase the duration.  I mean if you use a 3rd level spell slot to extend it's duration to 8 hours (or God forbid a 5TH level spell slot to extend it to 24hours), all that needs to happen is a lucky kobold arrow and a bad concentration save and it's all over.  I mean do you expect not to get hit in the next 8 (or 24) hours?  There are MUCH better 3rd, 4th and 5th level spells to use over Hunter's Mark to get an extra 1d6 until you fail a concentration save.  The extended duration element (for a spell that can be broken by a failed concentration save) by using a higher level spell slot is, in my opinion, stupid.  Like the only way this would be useful is if you don't plan to get into battle during this period and you just want to get Advantage when tracking... yeah, could be useful, but for a 3rd, 4th or 5th level spell slot?  Seems pretty expensive just for Advantage on a tracking check.  Or am I missing something?

I mean I get the whole concentration check thing if you are a wizard, behind the front lines being all "avoiding getting hit" and stuff like they are apt to do.  But if you are a melee ranger, digging in on the front lines hitting and getting hit, you are GOING to get hit and eventually lose concentration within 2-3 hits.  If you are going 8-24 hours without getting hit 2-3 times, what the hell are you doing?  This spell is not going to last more than 1, maybe 2 encounters (if you are really lucky).

Sure, it's a first level spell and at 11th level I have 4 spell slots for these per day, so if you get debuffed halfway into an encounter, no big deal, cast it again.  But please don't insult my intelligence as tell me that you are going to be able to maintain concentration for a spell that gives you combat/damage related buffs for 8-24 hours!  So lame… again, in MY opinion.  I could be wrong.

The Class Variant Options in last year's Unearthed Arcana fixes this, Rangers get it for free, no spell slot, doesn't count against your prepared spells, and best of all, doesn't use concentration.

 Do you have a link for the source I can't find this variant.

But it is a ranger spell

Quote from Dorpond >>

Quote from CaelVtroz >>

Does 'subsequent' mean next turn or any turn after so long as the concentration is still in effect?

 I would like to know this as well...

 It is any turn after because it says “a subsequent turn” instead of the subsequent turn the subsequent turn means the one directly after it was cast, but a subsequent turn means any turn after the one it was cast on but before the spell ends.

Do you need to be in range of 90ft of a other target when the one before gets his HP to 0? Can you choose a next target without using a spell slot when you find one within a hour of the last one having his HP reduced to 0?