Shatterfloor, particularly a Sculpted Shatterfloor.
Stone Shape is good for creating defensive barriers in area that have uh.. stone in them. Underground, for instance.
Talk to the DM if you can research versions of Entangle, Briar Web, Spike Stones and the like.
Wall of Ice is better than Wall of Fire, imo. Wall of Fire is a deterrant, Wall of Ice is a barrier.
Summoned Monsters, particularly ones that are good at grappling. Or Thoqqua. 'Cause Thoqqua rule.
Darkness (or fog) and summoned Assassin Vines.
Tasha's Uncontrollable Laughter. Otiluke's Resilient Sphere. With a thoqqua inside with the target. Did I mention thoqqua are awesome?
On the deterrant end of things - illusions. Particularly illusions of spinning barriers of whooshing, glinting. ginsu-your-ass-and-serve-you-up-in-a-stew blades. The up-side being the opponents arn't going to interract with it, because who in their right mind would stick themselves in a blender when you can just walk around it instead?
Fear on things with weak will saves. Ideally the kind of fear that makes the target drop stuff and run away in terror rather than just give 'em a case of the willies.
Blindness/Deafness, particularly on spell casters or archers.
Bestow Curse, particularly the "50% chance to lose your actions for this round" version. It's touch range though, so keep that in mind.
Cloud of Bewilderment, Belagarn's Iron Horn, and Shadow Well are all worth looking into (all from the PGtF)