The Magic Circle spell (which takes a minute to cast but lasts an hour) can be used in an inverted way:

When you cast this spell, you can elect to cause its magic to operate in the reverse direction, preventing a creature of the specified type from leaving the cylinder and protecting targets outside it.

Many planar entity conjuration spells, such as Conjure Woodland Beings, last up to exactly an hour, at which point the creature vanishes:

A summoned creature disappears when it drops to 0 hit points or when the spell ends.

Imagine the following scenario: Bob the Druid casts Conjure Woodland Beings, which makes DM-decided fey creatures (let's say 2 quicklings) appear, and maintains concentration on it. After 30 minutes, Dylan the Wizard decides to cast an inverted Magic Circle around one of the feys, which Bob orders to stand still. After that, Bob drops concentration on Conjure Woodland Beings. What I'm wondering here is what takes priority between "disappears when the spell ends" and "preventing a creature from leaving the cylinder".

Does an inverted Magic Circle prevent a Conjured Creature from vanishing at the end of its spell's duration?

If so, that means that the now-trapped fey is no longer friendly to / controlled by Bob, but remains there until the Magic Circle itself ends (total of 1 hour 31 minutes). If not, that means that the fey disappears as soon as Bob's concentration ends, regardless of the Magic Circle (total of 31 minutes).



The reversed Magic Circle needs to be read in context. In particular:

The creature can't willingly enter [leave] the cylinder by nonmagical means.

The creature is not willingly leaving so the spell does not prevent it.


Depends on whether they pass their saving throw

Consider this part of the spell description:

The creature can’t willingly enter the cylinder by nonmagical means. If the creature tries to use teleportation or interplanar travel to do so, it must first succeed on a Charisma saving throw.

If the spell is reversed then that should still apply in reverse. The creature can't leave the circle when the summoning spell runs out unless it makes a Charisma save.

  • \$\begingroup\$ I suppose the general view is that when the summoning spell ends the creature should automatically go back home. I stand by my answer though - the spell ending should try to send the creature back home and fail if they can't pass their save. \$\endgroup\$ – Allan Mills May 12 '19 at 0:55
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    \$\begingroup\$ @AllanMills it's not that the spell is sending it back home...rather the spell is now failing to keep in on the prime material plane \$\endgroup\$ – illustro May 12 '19 at 12:18
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    \$\begingroup\$ It's also not clear that the way the summoned creature is disappearing is by teleportation or interplanar travel (which are the only methods the spell prevents). Finally, it's not the creature trying to leave via those methods, it's someone else's spell failing to keep them on the current plane. \$\endgroup\$ – illustro May 12 '19 at 12:21
  • \$\begingroup\$ It may not be clear, but something has to happen to bring them to the material plane, and something has to happen to let them go back. That something is interplanar travel as far as I am concerned. I also don't read willingly as excluding non-willingly, but I accept that is my own interpretation. This answer would be correct in my world's however. \$\endgroup\$ – SeriousBri May 13 '19 at 9:43
  • \$\begingroup\$ @SeriousBri the summoned creature may be created from nothing. The game rules do not specify. \$\endgroup\$ – illustro May 14 '19 at 0:57

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