A Couple Custom D&D Spells

This was originally posted in 1997, when I was playing AD&D regularly, and apparently THAC0 was still a thing.

Melf's Acid Missiles (Invocation)
Level - 3
Duration - Instantaneous
Casting Time - 3
Area of Effect - One creature or object per missile
Range - as per magic missile
Components - VSM
Saving throw - 1/2 damage.

A cross between Melf's Acid Arrow and Magic Missile, this spell produces multiple missiles with an instantaneous acid splash, inflicting 2d4+1 points per missile, for one round only. Casters get one missile for every two (2) levels of experience, to a maximum of 5. At 9th level and higher, maximum damage potential is 45 points, median is 30 (for 5 missiles), minimum is 15. Comparable damage: Fireball (9th level) max 54, min 9, median 31.5.

Perimeter Watch (Abjuration)
Level - 4
Duration 1d6 hours + 1/2 hr per level
Casting time - 4
Area of Effect - 30' radius sphere
Range - 0
Components - VSM
Saving throw - none.

This spell establishes a circle around the caster (and his encampment) and alerts the caster when someone has entered this circle (who did not previously exit). It also gives him a general idea (within 90 degrees) in which direction the perimeter was broken. Perimeter Watch can detect creatures of one hit die or larger, or multiple creatures of less than one hit die. The perimeter, once broken, will only remain in effect for one round per level of the caster. Note that this spell will awaken the caster if necessary, but will not interrupt spellcasting in progress. The material component is a bit of string tied around a canine tooth.

Deception (Illusion/Phantasm)
Level - 5
Duration - 1d6 rounds + 1 round per level
Casting Time - 5
Area of Effect - The Caster
Range - 0
Components - VSM
Saving throw - none.

This spell creates 1d4 images of the caster plus an additional image per two levels, all of which seem to constantly shift, thereby making direct attacks virtually ineffective. If an image is attacked directly, the attack roll is made at a -4. Furthermore, when an image is attacked directly, it disappears, thereby making the process of finding the mage one of elimination. Area of effect attacks such as fireballs, etc., cause damage to the caster (when applicable), but do not cause any of the extra images to disappear unless the caster falls dead or unconscious. The target of a melee or missile attack is determined randomly from among the images, one of which is the actual caster. If the attack roll indicates a "hit" but not on the actual mage, one image is removed. If the mage casts any offensive-type spells, two images are removed. Note that illusionists get one extra image, and gnomish illusionists automatically get a 4 for their roll to determine how many images will appear. The material component is a clear, multi-faceted gem of at least 1000 gp in value, wrapped completely in a piece of fur from a displacer beast. Researched using Blur (Wiz:2), Mirror Image (Wiz:2) and Improved Phantasmal Force (Wiz:2).

Holl's Shadowdog (Conjuration/Summoning, Illusion/Phantasm)
Level - 6
Duration - 2 hours per level (max 48 hours)
Casting time - 6
Range - 0
Components - VSM
Saving throw - None

Casting this spell summons materials from the demiplane of shadow to come together in the form of a dog of the same alignment as the caster, that will act as both a travelling companion and a fierce guard dog. The dog will have a low intelligence and an empathic link with his summoner. If for any reason the dog loses all his hit points, he will be abjured back to the demiplane of shadow. The Shadowdog is 80% undetectable unless in bright light, where it suffers a -1 to attack and armor class. Note that this spell may only be cast once a day (DM determines the effects of multiple castings in one day), and that with each casting, there is a 1% chance that the shadowdog will become living. A living shadowdog loses one full hit die, but they gain the ability to heal their wounds overnight by licking them. If the caster is 16th level or higher, this chance increases to 5%. The following table determines the combat abilities of the shadowdog:

Caster Dog's
Level HD Thac0 # Att AC Damage
12-13 3+3 17 1 6 1d8
14-15 4+4 17 1 5 1d8+1
16-18 5+5 14 2 5 1d6+1
19+ 7+3 11 3 4 1d6+11d6+1/1d8+1

Note that Holl's Shadowdog and Mordenkainen's Faithful Hound will attack each other on "sight."