Wall of force

From Ardrana

A wall of force spell creates an invisible barrier in the locale desired by the caster. The wall of force cannot move and is totally unaffected by most spells. Likewise, the wall of force is not affected by blows, missiles, cold, heat, electricity, etc. The wizard can, if desired, form the wall into a spherical shape. The wall of force must be continuous and unbroken when formed.

Note: This version of wall of force originally appeared in the 2nd Edition Player's Handbook for Advanced Dungeons & Dragons from TSR. Its use here is for the purposes of providing context for the campaign only.