Energy Field

Energy Field is a name used to refer to several spells which create some sort of magical barrier. The older, Sosarian version of the spell is called Create.

Spell Description
Sometimes the caster needs to stop an enemy from advancing any further, and if no attack spells are available, the spell Energy Field comes in handy. It will create a solid energy field that none can pass, not even the caster themselves. Besides waiting for it to dissolve - which can take a long time - the only other way to get past it is the Dispel Field spell, which will destroy the field.

History
In the Age of Darkness, the spell Create was used within the confines of the dungeons to conjure a transparent, but impenetrable, wall of force. Although this barrier did not cause any damage, it effectively separated the caster from any creatures deemed undesirable to engage in combat. These walls could often be found already placed within the many dungeons of Sosaria, meant to impede progress or seal off sensitive areas. The Destroy spell could be used to remove any such barriers, whether created by the caster or otherwise.

Energy field research died off during the remaining Age of Darkness and only was revived in the Age of Enlightenment. During the early age, the term Energy Field was originally an umbrella term for all the types of magical fields: Poison Field, Fire Field, Sleep Field and Lightning Field, and the same spell would be used to create any of them. Later (after Ultima IV), different spells were designed for each of the fields, and the previous Lightning Field came to be known simply as Energy Field. However, at times the four spells are still called "energy field spells".

Trivia

 * In Mondain's Fortress, the spell actually works quite differently. Instead of creating force fields, it creates a small wall inside the castle. Together with the Destroy spell to dissolve wall parts, it is possible to lock in Mondain, thus making the final battle less tedious.