well I had a 20% forge site
and the Ultimate Gateway (50% Conjuration bonus) which kept me competitive even with a small income, few gems and low territory count. In the same province as the Ultimate gateway was Bottomless Lake with its 20% Conjuration bonus. But sadly they don't stack
But by the time I found the Gateway I was already boxed in by stronger powers on all sides and well behind in research and lands. So it couldn't win me the game. It did make me safe though, both because of all the cheap summons and because I could have used it as a threat to break up any alliance against me - as only one person could own it if I was beaten. As the weakest of the remaining powers I would obviously be the best person for everyone else to hold it if they didn't
By the end I was blood hunting quite heavily - getting about 90 a turn - but that was climbing. I had already bagged most of the Ice & Helios and was starting on the Demon Lords. I am not sure how strong Blood summons are though now everyone can spam Clensing Bells in CBM 1.6 I had a bunch ready for my fight with Abysia which never really happened so they never got used.