How do you handle "until next turn" effects with the Speed Factor Initiative Variant?

Question

The point of the Speed Factor variant is to make combat more unpredictable by varying turn order. From the DMG (p. 270):

Under this variant, the participants in a battle roll initiative every round.

Many actions--particularly spells, but also melee attacks like a monk's stunning blow--produce effects which last until the actor's next turn or impose a penalty on the opponent until the opponent's next turn. (Depending on the effect, it could be start of turn or end of turn.) But these rules seem to be designed to work with a fixed order of initiative, so that a combatant or an opponent gains the benefit or suffers the disadvantage for one turn.

If turn order can change from round to round, however, a character could cast a defensive spell on a low (late) initiative roll, then get a high (early) initiative roll the next round, have the effect expire, and never actually gain the defensive benefit. Conversely, a high (early) initiative roll followed by a low (late) initiative roll could give the character the benefit against two rounds of opponent attacks. Similarly for effects or conditions imposed on opponents, which might actually have no effective duration or twice the effective duration.

Since Speed Factor is a variant rule, I don't think there is a RAW answer (beyond "Them's the breaks"). Therefore I am interested in answers that include elements of the following:

1. Statements from authoritative sources (Sage Advice, other communications from game designers).
2. Rules as interpreted with evidence from the sourcebooks.
3. Actual experience in play, particularly if you have tried different approaches.
4. An evaluation of the impact of rules tweaks to reduce or otherwise handle the wide swing between no effect or double effect for effects that are supposed to last for one combatant's turn.

Note: A previous question about the variant initiative rules asks when to trigger certain class features (e.g. the monk's Perfect Self) that normally trigger at an initiative roll, given that under the variant rules initiative is rolled several times per encounter. The answer was essentially those features should trigger once at the beginning of the encounter. My question is about any effect that is measured in turns during combat (but especially those with a duration of 1 turn), and the answer to the previous question cannot be sensibly applied in this case.

Answer 1

This is not a problem for most effects. Most of them last “until the end of your next turn”, which for effects that benefit something you want to do on your next turn is plenty long enough.

The only case where that produces counterintuitive results is when an effect disadvantages your opponent, as in your defensive spell example or a monk's Stunning Strike, because if your next turn comes before they next act then the effect is “wasted”.

This second class of effects is easy enough to identify on-the-fly though. Since you're already using a variant rule, it's easy (and totally true to the spirit of the rules as written) to house rule that such effects last “until the end the next round”, giving a full round plus a few initiative counts of effect, fully covering the opponent's next action.

The only drawback of that is that it might cover more than one of your opponent's next turns, if the initiative counts fall that way. Why do I say that's a drawback? Because the enemy can do the same to you, if they use such an effect against you and the dice go their way. However, that makes it pretty fair: the PCs might occasionally get the double-dip benefit, but so can the enemy. And the dice are likely to more often go in the heroes' favour, since that's the overall design of the rules.

Answer 2

With the answers above, I see six variations, all of which have advantages and disadvantages. For a spell with a one round duration:

1. Goes with your initiative roll on each round. This is swingy, if you go first in round 1, and last in round 2, you get 2 rounds of impact. If you go last in round 1 and first in round 2 you get 0 rounds of effect (so 0-2 rounds of possible impact on each creature).

2. Spell is tied to your round 1 initiative count, so if your R1 init is 15, then the spell lasts until R2 init 15. Still swingy as per 1 (0-2 rounds of possible impact on each creature).

3. Spell starts R1 on your turn, but lasts until the end of R2. Less swingy (1-2 rounds of possible impact per creature).

4. Spell doesn't take effect until the start of R2 and lasts until the end of R2. Not swingy, but possible impact around being attacked after the spell is cast but before it takes effect.

5. Effect lasts until after n creatures are affected. So if you cast while 3rd in init order in R1, than it lasts until the 3rd person in R2. Not swingy in absolute number of creatures affected but still allows some creatures to be affected twice or not at all.

6. Effect starts in R1 as usual, but anyone not affected in R1 gets affected in R2 regardless on init order. Not swingy but possibly a nightmare to track and possibly confusing logically, area of effect spells, etc..

Answer 3

In normal combat without the variant rule, a round is a fixed unit of time (6 seconds), whereas a turn isn't so much a measure of time as the order in which your actions get resolved within that 6 second window. After all, if each turn truly represented a sequential block of time occurring within the 6 second window, participants would act faster with more people in the initiative order, which doesn't really make sense. It is for this reason, that no durations are measured in numbers of turns, as a turn isn't truly a measure of time.

Nowhere in the speed factor description does it modify the length of time that makes up a round. Additionally, every participant still gets 1 turn in each six second round, so the notion of order in which effects resolve as opposed to subdivisions of time within the round is preserved.

Why is this important? In your example, the defensive spell that lasts until the end of your next turn, such as the Blade Ward spell, the duration of time is explicit. The spell's Duration is listed at 1 round, which is established to be 6 seconds no matter if you are using speed factor or not. Moreover, the description says the spell lasts until the end of your next turn; in standard initiative this is always a fixed period of time (one round) since your initiative is fixed in the same spot every round. So in Speed Factor variant initiative, I think it is pretty clear that the duration of the spell would remain the same, at 1 round. The spell would not necessarily expire at the end of your next turn, but instead after 1 round had elapsed since the point you cast the spell, whether you occupy that place in initiative order any more or not. In short, whenever you see "until the end/beginning of your next turn", it means in the Speed Factor Variant that the effect lasts until the end/beginning of the turn that you occupied in the initiative order the last round when the effect was created. This results in an effect maintaining its duration between vanilla initiative and variant initiative.

There is another case that you do not mention, but is probably worth addressing - when an effect lasts until an target's next turn, such as the inability to make reactions with the Arm's of Hadar spell. In this circumstance, the effect in vanilla is a variable duration of time less than 1 round, as 2 creatures effected by this spell will have the effect expire for them at different times within the round (on each of their respective turns). Since this duration is already variable, I would suggest keeping it as such in the Speed Factor variant. In my mind this type of duration seems to indicate an effect that a target manually shakes itself out of when it resolves its action in initiative order; but even if you don't share in this thinking, there is no explicit duration mentioned in the description, so the duration of the effect should be handled as written.