Duo-Dimension

A duo-dimension spell causes the caster to have only two dimensions, height and width but no depth. 

He or she is thus invisible when a sideways turn is made, and this invisibility can only be detected by means of a true seeing spell or similar means. In addition, the duo-dimensional magic-user can pass through the thinnest of spaces as long as they have the proper height according to his or her actual length—going through the space between a door and its frame is a simple matter.

The magic-user can perform all actions on a normal basis. He or she can turn and become invisible, move in this state, and appear again next round and cast a spell, disappearing on the following round. 

Note that when turned the magic-user cannot be affected by any form of attack, but when visible he or she is subject to triple the amount of damage normal for an attack form, ie. a dagger thrust would inflict 3-12 hit points of damage if it struck a duo-dimensional magic-user. 

Furthermore, the magic-user has a portion of his or her existence on the Astral Plane when the spell is in effect, and he or she is subject to possible notice from creatures thereupon. If noticed, it is 25% probable that the magic-user will be entirely brought to the Astral Plane by attack from the astral creature.

The material components of this spell are a thin, flat ivory likeness of the spell caster (which must be of finest workmanship, gold filigreed, and enameled and gem-studded at an average cost of 5,000 to 10,000 g.p.) and a strip of parchment. As the spell is uttered, the parchment is given a half twist and joined at the ends. The figurine is then passed through the parchment loop, and both disappear forever.

See APPENDIX C: RANDOM MONSTER ENCOUNTERS, ASTRAL & ETHEREAL ENCOUNTER TABLES.