The 2nd-level Sor/Wiz spell indifference [ench] (Tome and Blood 92 and—so far as I'm aware—never reprinted), in part, says
This spell drains emotion from the creature touched. The subject becomes immune to fear and compulsion effects of 2nd level or lower and gains a +4 circumstance modifier on saving throws against fear or compulsion effects of 3rd level or higher. Furthermore, morale bonuses or penalties do not affect the subject while the spell lasts.… (92)
How does this spell interact with effects that lack a spell level?
For example, a creature that's immune to fear can't be intimidated (Player's Handbook 77). Would the subject of the indifference spell be immune to Intimidate skill checks made to demoralize the subject?
Note: Why, yes, I am looking for inexpensive alternatives to feats—like the Player's Guide to Faerûn regional feat Fearless (38)—that smart NPCs can use to defend themselves against the feat Imperious Command. The spell indifference has several advantages over other low-level (hence inexpensive) spells I've found like the remove fear spell, but I'm unsure of how the indifference spell works in this regard and wondering if guidelines exist for adjudicating this kind of corner case. I am aware that as the DM, I can make "minor adjustments" to unresvised dnd-3e material for my dnd-3.5e campaign as per the Dungeon Master's Guide on Why a Revision? (4), but I'd rather have community input before ruling unilaterally. Also, if it turns out that the indifference spell is useless against mundane fear effects, I'll pose another question; answers to this question are a lousy venue for a list of methods to hinder the feat Imperious Command.