This is in reference to Does casting a long spell end a maintained Concentration spell?

Casting spells that take more than an action require concentration, so this means you have to drop your concentration spell to cast them.

Slow can make spells take more than one action, does this mean that if my wizard has Detect Magic up, is affected by Slow and casts Magic Missile (which now takes longer than one action to complete); do I pick if the Magic Missile goes off or the Detect Magic is dropped?

  • \$\begingroup\$ This is a great question. Just to confirm, I think you are seeking an answer based on RAW? Is that correct? \$\endgroup\$ Aug 8, 2017 at 15:27
  • \$\begingroup\$ something that is good enough for AL \$\endgroup\$
    – Bas Hamer
    Aug 8, 2017 at 21:13

2 Answers 2


Casting Time is not affected by Slow

Casting Time is an attribute of a spell, just as Speed is an attribute of a character. The Slow spell reads:

If the creature attempts to cast a spell with a casting time of 1 action, roll a d20. On an 11 or higher, the spell doesn't take effect until the creature's next turn, and the creature must use its action on that turn to complete the spell. If it can't, the spell is wasted.

If the Slow spell was meant to alter the Casting Time, the authors would have used the much simpler construction, "On an 11 or higher, the spell has a Casting Time of 2 Actions."

The rules mean exactly what they say: the Casting Time remains 1 action, but the spell does not take effect until the next round, and the creature must use a second action to complete (not "cast") the spell.

Note that the Slow spell affects up to six creatures in a 40' cube at the rather hefty range of 120'. To be able to potentially bring down the concentration spells (or otherwise prevent further castings) of so many enemies at such range and area would be pretty impressive for a mere third level spell. Even with this less generous interpretation, Slow roughly halves the casting power of a typical spellcaster and similarly halves the firepower of most other classes. As written, Slow is an outstanding spell and hardly needs any further buffing to be worth a page in every wizards' spellbook.

  • 3
    \$\begingroup\$ the problem with this logic is rituals; rituals state that the spell takes "10 minutes longer to cast", not a casting time of 10 minutes. If something takes an extra action or an extra 100 actions should not change the type of increase. \$\endgroup\$
    – Bas Hamer
    Aug 8, 2017 at 21:17
  • \$\begingroup\$ @BasHamer Rituals are explicitly called out in the section on "Longer Casting Times". That would not be necessary under the alternative logic, but is necessary under this interpretation. \$\endgroup\$
    – pokep
    Aug 8, 2017 at 21:35

Longer Casting Times doesn't make any exceptions for the cause of the longer casting time; if it takes more than a single action or a reaction, it requires concentration.

Concentration says you lose concentration on a spell if you cast another spell that requires concentration. You can't concentrate on two spells at once.

The only choice is starting to cast another spell, or not. If you start another spell that requires concentration, concentration on the first spell is lost. What causes the second spell to require concentration is not a factor.

Slow has a 50% chance to turn a single action spell into a multiple action spell. As the character doesn't know exactly how long the spell will take, if they risk it, they risk suffering the consequences. The player can decide if the character wants to take the chance.

  • \$\begingroup\$ my main problem with this answer is that you can "end concentration at any time (no action required)." I don't see anything backing that you don't choose. It is as if there is a weird time loop, concentration ends at the start of an action, but you don't know if the action satisfies the conditions until after it starts. \$\endgroup\$
    – Bas Hamer
    Aug 8, 2017 at 21:23

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .