Bound Circle

When you cast this spell, you create a circle on the ground, drawing arcane sigils in a 10 foot radius circle; the area forms an invisible 30 foot tall cylinder (the top of which is closed off). This spell was designed to prevent harm from certain entities; elementals, fey, fiends, and undead find that they cannot cross into such an area or target any creatures within its area with attacks, spells, or abilities. If such a creature casts a spell or has an ability whose area extends into the cylinder, the effect is nullified for all those within the cylinder (eg a fireball's flames would flow harmlessly around it). Extraplanar travel and teleportation into and out of the circle is blocked.

If the circle is broken, either by being smudged by an occupant of the circle, or if a creature leaves the circle, the spell immediately ends.

The circle can be inverted when cast, made to keep such entities inside of it. These entities cannot affect the area outside the circle without the permission of the caster.

If this spell is cast in the same place for a year and a day, it becomes permanent. The circle, after this point, can be triggered by an activation word of your choice. Typically this is done by inlaying a surface with the casting components so that it cannot be smudged. Stepping outside of it ends its effects, but simply speaking the command word again reinitiates it.