Build-a-spell analysis of the last group of LBB Magic-User spells. I expect these spells to make the least sense in a component analysis sense; other spells might accidentally fit perfectly into a 1 feature = 1 level scheme, but 6th level spells were originally the most powerful spells possible, so the spell list was probably developed by asking "what's the most powerful magic in myth, legend, and fairy tale?" Anything that fit in that category was automatically assigned to 6th level. This is thus where the really large-scale physical changes wind up, as well as the instant kill or spells to cheat death.
Stone to Flesh is "immobilize opponent", "transform flesh", "permanent until dispelled", "only dispelled by reverse", and "can affect larger than man-sized opponents". In theory, the reverse has fewer features and should be a lower level, but since the two spells only count as one for learning purposes, that can be considered a side effect. Add variable range for 5 Features + 1 Variable = 6th level spell.
Reincarnation creates a body of randomly-determined form, makes it alive, transfers the memories and personality (spirit/soul) of a deceased character, potentially makes the character more powerful than before, makes it permanent, can't be dispelled. That's 6 Features, for a 6th level spell.
Invisible Stalker can be built up from Conjure Elemental, if we consider the duration feature to be worth double, since a stalker can't be dispelled, but must complete its mission.
Lower Water and Part Water might be underpowered, even if we count "large volume" and "large area" as double because of the wide scale. We can change the duration to a variable to compensate, though.
Projected Image creates an illusion, allows senses to be used at the other location, can be moved, can speak/cast spells from new location, and can't be dispelled by touch (at least, it's not mentioned in the LBBs, as it is for Phantasmal Forces.) Change the range to a variable and we have 5 Features + 1 Variable = 6th level spell.
Anti-Magic Shell is probably easiest to visualize as "blocks spells of level 1-6", one feature per spell level. Nothing else is listed as variable, and the duration/area seems to be pretty small. Of course, if we weren't restricting ourselves to a level 6 cap, we'd either need to build this some other way, or add a "Greater Anti-Magic Shell" at a higher level.
Death Spell injures without the need for a weapon, injury is instant death, affects multiple targets; the spell is also usable at a distance. There's really not much left to work with, to make up for the two "missing" levels, other than the spell only affecting creatures with HD <= spell level.
Geas can be built off Charm Person (1st level spell,) with an open-ended duration that only ends when dispelled or the task is completed (2 Features.) Weakness for those deviating from the task and death for ignoring the task are worth 2 more features, plus a "no saving throw" feature for the death effect.
Disintegrate damages a target and leaves no residue (2 Features,) kills a living target, target can be larger than man-sized, there's no limit to size, and caster can choose to disintegrate only part of a target. 6 Features = 6th level spell.
Move Earth affects an area on a wide scale, which can be considered to be 2 Features. The movement is at a reasonably quick speed (armored human speed,) affects a larger than human size, and has no limit on size (can move either a low hill or a high hill.) Variable range can be added to make up the missing level. 5 Features + 1 Variable = 6th spell level.
Control Weather affects three weather features (temperature, wind, percipitation) for a period of hours to days over a wide area. If the area feature counts as two features because of the extremely large scale, that makes 6 Features, for a 6th level spell.
I'll have a follow-up post on lessons learned from this analysis, plus a post or two on other spell lists.