On the other hand, not all judges have the resources (i.e., the stupidly large library of adventures coupled with knowing which adventures include which monsters) to simply look these up. So I am going to create a usable imp without referencing the existing work, but I will also urge you to consider this as a secondary statblock at best. On the other hand, “Make Monsters Mysterious” allows you to use both!
In Ye Olden Days, when I just had the Dungeon Master’s Guide to reference, and the Monster Manual was still on my wish list, I had a very different idea of what an “invisible stalker” was. The invisible companion spell covers the Monster Manual version very well. What you are getting here is, to the best of my memory, what I envisioned.
Imp: Init +3; Atk tail sting +2 melee (1d4 plus venom); AC 18; HD 2d12; MV 20’ or fly 60’; Act 1d20; SP venom (1d4 Stamina damage plus DC 13 Fort or 3d6 damage), alternate shape, regenerate 1/round, detect magic 120’, invisible at will, familiar; SV Fort +1, Ref +5, Will +4; AL L.
These devilkin are found in the Hells, but are occasionally
sent to the Lands We Know in order to spread evil among mortal beings. In its
own form, an imp appears as a winged diabolical humanoid, about two feet tall,
with a venomous sting on its tail, but each imp can also take on 1d3 of the
following shapes, using appropriate AC, attacks, and saves when in that shape:
(1) large spider, (2) raven, (3) giant rat, or (4) goat.
Regardless of form, an imp regenerates 1 hit point per round (but is dispelled and return to Hell at 0 hp), can become invisible at will, and detects magic at a range of 120’. An imp can bond with a cleric, wizard, or elf in a manner similar to a diabolic familiar, and with the exception of the statistics above is otherwise treated as such once bonded. No find familiar spell is required, jus an agreement between the two parties which consigns the master’s soul to Hell upon their death.
Intellect
Devourer: Init +2; Atk claw +3 melee (1d4) or psychic attack; AC 16; HD
6d8; MV 40’; Act 4d20; SP psychic attack (1d4 Intelligence and Personality
damage, Will DC 16 negates), consume thoughts, sense psychic energy 60’, possession,
stealth +14, immunity to most weapons and physical magic, electrical
vulnerability, light vulnerability, planar awareness and travel; SV Fort +4,
Ref +2, Will +8; AL C.
Worse, intellect devourers are immune to most weapons and magical attacks. Magical weapons do their bonus damage only (i.e., a +3 weapon does 3 hp damage) plus any damage from Mighty Deeds or critical hits. Magic normally causing physical damage sloughs off intellect devourers without effect, save electricity-based spells or attack, which cause only the minimum possible damage. Magic which affects the mind (including protection from evil) affects intellect devourers normally.
If a creature uses psychic energy within 60’ of an intellect devourer (which includes mind-affecting spells, psionic powers, and mental mutations) the monster awakens from its semi-dormant state and begins to stalk its victim. An intellect devourer seeks to get its victim alone, and, if it manages to reduce the victim’s Intelligence or Personality to 0, it can possess its victim’s body. It then pretends to be its original victim, and seeks new victims. No matter how far an intellect devourer is from its original body it can return with one round of concentration, leaving its victim permanently impaired unless magic is used to restore the lost Intelligence and Personality.
(If a victim is reduced to 0 Intelligence or Personality, and an intellect devourer is prevented from possessing it, the attribute damage heals normally. Once possession has occurred, it is permanent.)
Bright light causes intellect devourers intense pain, although they are not hurt from it, and the creatures flee from light sources brighter than a lantern. Magic which could not otherwise hurt an intellect devourer but which causes bright light (such as color spray or fireball) forced the monster to succeed in a morale check or flee. An aversion to bright light remains in possessed victims, which sometimes gives an intellect devourer away.
Because of this aversion, intellect devourers are only found dwelling deep beneath the ground or in dark and dismal lairs in the wilderness. Their awareness extends to the astral and ethereal planes, and intellect devourers often roam these places in search of prey.
Invisible
Stalker: Init +4; Atk bite +2 melee (4d4); AC 17; HD 4d8; MV 30’; Act
1d20; SP invisible, +10 stealth, 30% magic resistance, death throes; SV Fort +4,
Ref +8, Will +3; AL N.
This terrible creature is sometimes found lairing in dungeons or ruins, but those misfortunate enough to encounter it seldom know for certain what it is they encountered. For those who can see it, this creature looks like a great cat, 8 feet long, with an oversized maw.
Invisible stalkers are often unaffected by magic (roll this chance before any applicable saving throw), allowing them to potentially ignore spells (including detect invisible and similar spells) and pass through magical barriers with ease. Because of their stealth and their invisibility, they can often gain a surprise round, and enjoy toying with their prey by attacking and withdrawing, much as a cat might allow a mouse some temporary reprieve.
When an invisible stalker is slain, its body evaporates into the ether, leaving nothing behind to hint at its physical form.
Irish Deer: See the Cyclopedia of Common Animals.
Ixitxachitl: See the entry for manta rays in the Cyclopedia of Common Animals for a substitute for this monster.