Attempting to summarize it all...
Paradox (Su): Instead of using its energy drain, a temporal stalker may choose to instead alter one aspect of the victim's past made within the last 24 hours. A successful DC X Will save negates this effect. The save DC is Charisma-based.
When using paradox, a temporal stalker may choose one of the following effects:
Recall Agony: The paradox reveals wounds the victim has received in the past. That foe takes 2d6 points of damage as the past impinges briefly on the present.
Spell Swap: The stalker may swap out one of a spellcaster's prepared spells for one less useful in the current battle. To do so, the temporal stalker makes a Spellcraft check opposed by the victim's caster level + 10. For each point by which the stalker beats the DC, it may replace one spell level. Thus, a stalker beating the DC by 7 could replace a single spell of up to 7th-level. Spell swap has no effect on spontaneous casters.
Switch Item: The stalker may alter an single item worn or carried by the victim with another item on its person. Thus, it could swap the vial of holy water its victim holds with a flask of acid from its backpack, or replace its drawn magic longsword with a fork from its mess kit. The replaced item always returns to the most logical place on the victim (a weapon back to its sheath, tools back to a backpack, spell components back to a pouch, etc.)
I also propose we add a fourth option for dealing with spontaneous spellcasters, the ability to swap out an ongoing spell effect with another in its arsenal. Thus, shield could be replaced with protection from energy, or bull's strength with owl's wisdom, for example.