Nice work Tim, thanks for sharing
As I mentioned over on the G+ group, I did a version of the same way way back when DD was still being put together. I've unearthed my notes and tidied it up a bit and here it is...
MIND FLAYERS (1-4) [AC 7 MV 12" HD 7+1 50% TT F C] are super-intelligent, absolutely evil, man-like monsters with four tentacles surrounding the ghastly mouth. They abhor sunlight and dwell only deep underground, and will always flee rather than risk facing a genuine threat. However, a mind flayer is a dreadful foe who is 83% magic-resistant and can either attack physically or generate a mental mind blast each turn.
The mind blast will affect 2-9 man-types in a 6" deep arc before the monster. Those nearest the mind flayer are always affected first, sheltering those further back. Normal types are immediately rendered unconscious. Heroic types are allowed a save versus spells with failure indicating they are
Confused; superheroic types who fail to save are instead
Feebleminded.
In physical combat, a mind flayer can automatically lash its foul tentacles to the face of a prone man-type, otherwise requiring an attack roll that exceeds the number required to hit by 4 or more, or is a 20, to do so. Unless the mind flayer is interrupted (by being hit, for example) the victim's brain will be sucked out and devoured in the following turn; slaying him. Normal types observing this horrible death must make an immediate morale check at -2.
---- Notes ----
. Based largely on the Mind Flayer from Strategic Review 1.1 (Mar-May, 1975).
. The original AC 5 implies mail armor type, but the original movement 12" implies leather armor type,
. 90% Magic Resistance is "introduced" without explanation, but remember that Balrogs (not cut from 3LBBs until 1977) also had 75% MR,
. "Mind Blast, a wave of PSI force" appears prior to the official psionics rules (which appeared in EW, Apr 1976),
. Rewriting the saving throw table by intelligence rather than by level is an added complexity which was cut from the AD&D Mind Flayer.
My version is reduced to AC 7 (from 5), which seems appropriate for a fleshy M-U type with 12" movement, and to 7+1 (from 8+3) HD which is equivalent to an 11th level M-U in DD. Magic resistance is reduced marginally to 5/6ths for no compelling reason, and potency of the mind blast is possibly reduced somewhat vs normal int. higher level figures, but increased somewhat vs lower level types by switching back to regular ol' level-based saving throws.
Dicing for the number of figures affected by the mind blast is a convenient abstraction that forgoes the need for an accurate map of figure positions. But assuming we
did have figures positioned on a scale battlefield map, how many man-types could possibly be affected by a 5ft wide x 60ft long cone? According to S&S (p2), men equipped with daggers, spears, axes, maces, short-sword, etc. each require 6¼ft of fighting space, so not more than 9 men could fight along a 60ft wide front. Not more than 4 men equipped with two-handed swords could fight along the same front. Therefore at
most 9 men could be affected, assuming they are as tightly formed as possible. Player types are unlikely to be this tightly formed (although mercenary spearmen might be) so 2-9 men seemed to be "about right".
I also had an undeveloped note to the effect that Mind Flayers have unlimited use of
ESP, and that
ESPing a Mind Flayer is equivalent to being mind blasted by one.
FWIW, I would have them replace Mastodons on Dungeon Encounter Table 5 (col 2 row 16 of Table 2.6, p49 of the Ref Rules Compendium).
Enjoy