I was under the impression that Zeltrech was the one who set everything up, pulling the combined efforts of the Matou, Tohsaka and Einzberns together.
Nope, he pretty much was just a teacher of the Tohsaka, I think a generation or two before the War ever even started. It was the Einzberns that really wanted it, and they brought Makiri and Tohsaka in.
Zelretch gets involved at random intervals for the hellofit, though, he's a whimsical guy like that.
His only semi-direct involvement in the War was that Rin had Shirou fake his sword to fight Sakura, and he came along to congratulate her on getting so far with the hints he'd left for the Tohsaka.
(Though whatever his involvement, we can only be glad he was. Otherwise no Kalediostick and thus no Magical Ruby!)
(Coughs at making Ranma a magical girl)
There is no problem that cannot be solved through the proper application of immense levels of firepower.
- Finally promoted to Spammaster Indeterminate Rank as of June 18, by Stratagemini
<Stratagemini> My Titanium Anus Armour will repel all challengers!
Would you believe this is one of the more tame bits of dirt I've got for him?