Detect Invisible (Objects): A spell to find secreted treasure hidden by an Invisibility spell (see below). It will also locate invisible creatures. Durations: 6 turns. Range: 1" x the level of the Magic-User casting it, i.e. a "Wizard" would have a range of 11", more if he was above the base value.These are contrasting spells; Detect Invisible finds something hidden by magic without the caster needing to know what to look for, while Locate Object can find any general purpose items, like stairs up, the nearest door, or a generic container. The first gives exact location, presumably allowing the caster to see the object; the second gives only direction and does not provide details.
Locate Object: In order for this spell to be effective it must be cast with certain knowledge of what is to be located. Thus, the exact nature, dimensions, coloring, etc. of some magical item would have to be known in order for the spell to work. Well-known objects such as a flight of stairs leading upwards can be detected with this spell however. The spell gives the user the direction of the object desired but not the distance. The desired object must be within range. Range: 6" + 1 "/level of the Magic-User employing the spell, i.e. a "Necromancer" has a 16" range.
For Locate Object, "Magic Item" is specifically excluded from items that can be found, and presumably "Treasure Chest" would be as well; you can search for a general class of item without specific details like "magical" or "gold", or you can look for a specific item that you know all the details about already. Thus, it can be used to find one of your own possessions that has been lost, or find your way back to a landmark you've seen before, but it's useless for finding highly useful specific items.
Detect Evil: A spell to detect evil thought or intent in any creature or evilly enchanted object. Note that poison, for example, is neither good nor evil. Duration: 2 turns. Range: 6".There's a distinction here between detecting a specific thought (evil intent) and the presence of thought in general. I'd suggest that Detect Evil is to ESP as Detect Invisible is to Locate Object: Detect Evil finds the location (in one or more creatures) of evil, while ESP finds the direction towards one or more thinking creatures. Detect Evil doesn't work if you can't see the creature or object, and ESP doesn't identify what kind of creature you've located.
ESP: A spell which allows the user to detect the thoughts (if any) of whatever lurks behind doors or in the darkness. It can penetrate solid rock up to about 2' in thickness, but a thin coating of lead will prevent its penetration. Duration: 12 turns. Range: 6"
I don't think either spell is intended to act like telepathy; there's no communication of the content of a creature's thought, only whether a creature is evil or is a thinking being. I'd allow Detect Evil to detect general types of evil (brooding, wrathful, scheming, violent, envious) and ESP to detect general topics and number of creatures (three hungry beings behind the door, alert and cautious creature around the corner.)
Note, also, that the specification of thought or intent emphasizes that Detect Evil is not Detect Chaos or Detect Alignment; evil is what a creature does or plans to do, not an innate "taint". This has a bearing on the Clerical version of Detect Evil, since it's reversible. Traditionally, later editions make Detect Good the reverse of Detect Evil, but if "evil" refers to thought or intent, what is "good"? "You sense that the goblin is planning to help you"? Why would this be considered an anti-cleric's spell? Perhaps the reverse ought to be Conceal Evil instead, hiding the intent of a creature or enchanted object.
Duration is varied for each spell. Locate Object has no duration specified, so perhaps the duration is immediate, which would fit with Detect Magic. However, that dramatically shortens ESP, and lowers Detect Invisible and (Clerical) Detect Evil as well. Perhaps we can make a distinction between spells that alter the caster's observation ability (Detect Invisible, ESP) and those that reveal a property of the target ("magic" for Detect Magic, "direction" for Locate Object.) This still have the side effect of cutting the duration of ESP in half, but that's not as extreme as shortening it to one turn. Also, it allows us to make a distinction between M-U Detect Evil (reveals property) and Clerical Detect Evil (gives ability to perceive evil for 6 turns.)
Range is 60 feet for the "thought" spells, 60 feet + 10 feet/caster level for Locate Object, and 10 feet/caster level for Detect Invisible. The 60 feet range is about the size of a large room, so it's a shorter distance than Charm Person/Sleep, but not as short as the proposed "Close" range of 10 feet/spell level. I think we're seeing three range categories here:
- non-combat: 10 feet/spell level
- pre-combat: 60 feet (+ 10 feet/caster level?)
- combat: line of sight, minimum 240 feet/three spell levels