Comparison between Insubstantiality and Astral Projection
 

I'm going to set the spells out here and see if a discussion of what situations would warrant the use of one over the other. The biggest thing would be the lack of movement with and coverage area for Insubstantiality.

Astral Projection (S) is an IQ 15 spell on ITL, page 28. Cost 10 ST and lasts 1 hour.

Insubstantiality (T) is an IQ 17 spell on ITL, page 31. Costs 4 ST +2 to maintain.

I can't see where Insubstantiality is more powerful than Astral Projection to warranty it being an IQ 17 spell. The fact that one is a Special spell and the other is a Thrown spell creates a tactical difference. Even so, it still seems that Insubstantiality is far too expensive for what it delivers as opposed to Astral Projection.

In my Classic TFT days. I saw both used. Insubstantiality did seem to lend itself to more tactical use during battle. Astral Projection must be cast by a character that is far away from the battle because the body is a sitting duck if he has no body guards.

What do you all think?

I do suspect that Astral Projection may have been present in some of my more recent Legacy TFT sessions as a player.

Re: Comparison between Insubstantiality and Astral Projection
 

That comparison is interesting, worthy of its own thread, and is outside the scope of this one.

Re: Comparison between Insubstantiality and Astral Projection
 

I agree that Insubstantiality doesn't offer much for the cost. The movement limits built into it detract from its practicality. Teleport (IQ 15, Special) can often be a better alternative--certainly less costly per hex traversed.

One important difference is that Insubstantiality can be cast on someone other than the wizard to temporarily diminish an opponent's offensive and motive capabilities, whereas Astral Projection and Teleport can't. Is this worth a typical cost of at least 6 ST? Probably not. Giant Rope costs less, doesn't suffer a range penalty (though is limited to a few hexes), puts a crimp in the subject's style, and, unlike Insubstantiality, can't be defended against by Spell Shield.

Re: Comparison between Insubstantiality and Astral Projection
 

Perhaps, it's an unfair comparison. I always saw them as being similar with respect to how the subject of the cast spell interacts with their surroundings.
In fact, the thread about Astral Projection had me confusing these two spells until I read the spells. It had been so long since I had seen either used that I had confounded them together in my aging mind.

Re: Comparison between Insubstantiality and Astral Projection
 

How about this?

If you want to know what's on the other side of a locked vault door, Insubstantiality will do the trick quite nicely. Most of those who've given an opinion don't reckon that Astral Projection is useful for this task.

I think there are a number of times where the cost of Insubstantiality is worth it. But probably few of those are in the throes of combat.