There are 8 spells of 6th level for illusionists in AD&D, up from 6 in OD&D. Shadow Monsters III has been renamed to shades, demi-shadow magic has been brought up from 5th level, and veil is brand new.
Conjure Animals: Like the 6th-level cleric spell, it allows the caster to summon a number of animals whose total Hit Dice are equal to the level of the caster. It has a duration of 1 round/level (vs. 2 rounds/level for clerics) and a casting time of 6 segments (vs. 9 for clerics.) I find the actual conjuring of for-real creatures somewhat of an odd fit for illusionists. Doesn't it go against the theme a bit? I suppose stage magicians are always pulling animals out of things though, so maybe it's fine.
The OD&D version of the spell wasn't limited by Hit Dice. It allowed the caster to summon one creature the size of an elephant, three the size of bears, or six the size of wolves.
Demi-Shadow Magic: The spell works like shadow magic (detailed in my last post), but it also allows the illusionist to cast quasi-real versions of wall of fire, wall of ice or cloudkill. As with shadow magic, the spells function as though real to anyone who fails their saving throw. Against anyone who makes it, the damage is reduced, and in the case of cloudkill it will only kill creatures with less than 2 Hit Dice. It can still be used to cast the same spells as shadow magic, but they now deal 2 points of damage per level instead of 1 against those who make their save.
The OD&D version of the spell was the same in that it dealt more damage then the weaker version of the spell. It didn't allow for the casting of magic missile, cone of cold, or cloudkill. The original spell allowed the casting of death spell, which seems to have been replaced by cloudkill.
Mass Suggestion: This works like the suggestion spell, but it affects one creature per level, as long as they're all within 3" of the caster. Every target is under the same suggestion. If cast on a single target, there's a penalty to their saving throw.
The OD&D spell was the same, but it affected 1d8 targets rather than one per level.
Permanent Illusion: Like spectral force, it creates an illusion of a creature or object with visual, sound, smell, and thermal elements. The main difference is that the illusion is permanent, requiring no concentration from the caster.
The OD&D spell was exactly the same.
Programmed Illusion: This spell sets up a spectral force that is triggered by certain conditions, and last for 1 round/level.
The OD&D spell had a flat duration of 12 turns, rather than 1 round/level.
Shades: Similar to shadow monsters and demi-shadow monsters, but the creatures created are 60% real.
In OD&D this spell was called shadow monsters III. It granted creatures a base AC of 7 (whereas the AD&D spell remains at AC 10), and allowed the creation of a total Hit Dice equal to double the illusionist's level (in AD&D it still remains equal to the caster's level).
True Sight: Like the 5th-level cleric spell (called true seeing), it allows the caster to everything within range in its true form, regardless of illusions, polymorphs, and other forms of disguise. Unlike the cleric spell, the illusionist isn't able to discern alignment. The illusionist spell has a range of 6" (vs. 12" for clerics) and a casting time of 1 round (vs. 8 segments). Illusionists don't require any material components.
The OD&D spell allowed the caster to discern alignment, class, level and the intentions of any target. I'm not surprised that Gary jettisoned all of that. It also had a complicated duration formula of the character's level minus 10, + 1d6 rounds. In AD&D it's a simple 1 round/level.
Veil: The caster is able to change the visuals of their surroundings and/or their party. These illusions can be touched without disappearing, and will only be penetrated by true seeing, a gem of seeing, or the like.
As you may have noticed, I'm powering through these entries as quickly as possible. I started detailing these spells all the way back in 2016, and once I got started I felt obligated to see it the whole way through, regardless of how tedious it got. Well, the end is quite literally in sight: I'm finally at a page in my PHB where the spell entries are done. For those of you who followed me through this, thank you. It should be quite a while before I do something like this again: I'm thinking it'll be when I hit the Moldvay Basic Set, and obviously that won't be anywhere near as long. Regardless, I'm glad to be almost done. It can only get more interesting from here.