The Priori Incantatem effect of the brother wands meeting certainly seems based on Priori Incantato (though why was never explained that I could recall) and that one certainly did go back further than just the last spell.
The Priori Incantatem effect of the brother wands meeting certainly seems based on Priori Incantato (though why was never explained that I could recall) and that one certainly did go back further than just the last spell.