There aren't a lot of sacrifice spells to create a transformation effect. Druid coronet is an example.
Could check off all 0-level spells in training room (UR players don't likely care about training room) for some sort of dungeon wide buff. Or, 1st level spells. Or, N number of spells of some level.
It does sound kind of clunky in practice, so maybe go with something more like coronet where it's one room player option.
Shirt of Divine Aid
Cleric, Druid
Sacrifice two 1st-level spells. Party members gain +2 saves, +2 to hit, & heal 10hp.
That seems kind of boring, it's just converting spells into other spells. More interesting and also more applicable to wizards than healing would be creating a continuous damage reduction effect for the room. That also could be used against puzzle damage. Would be a larger effect than the (base) healing output that could be generated with same slots.
Another possibility is saccing spells for resurrection, but that's weird thematically in that it's a much higher level effect than 4th/5th level clerics/druids, yet, yet, we have potions all over the place this year which will bring someone back.
Can go the other way, too, which would be highly Grind relevant. Do like Crown of Expertise but focus more on restoring spells (all 0-level, for instance). Of course, the problem with unchecking boxes is that a lot of the black marks don't rub off.
Only vaguely a UR level effect but could have a token decrease one save to increase another by significantly more (kind of like messing with Dex/Con but different design space and less OP). This gives players an opportunity to either balance saves or unbalance them to their interest. I've played a paladin with a 27 Dex Save. +5/-2 to move to, say, Will ... is probably so irrelevant to UR level players that it would never get used.
I'd like to see paladin get to cast spells, something that is probably not around the corner. That's tricky, of course, to implement through a token.
Figurine of Power: Honey Badger
Set hp to 1pt if Push damage would kill wearer
Can do similar thing with puzzle damage.
Was mentioned as something for barbarian, but could generally create MEC like effects for melee/missile types (especially melee).
Maybe not an UR effect (though maybe is to prevent widespread use) - solve a puzzle triggers benefit, like healing (duplicating scroll effect from last year) or restoring abilities/spells (black mark problem) or resurrection (limit this a lot, also kind of more relevant below UR level).