City of Infinity. Parallel Society, #7

For Veronica "Roni" Ryder, the journey to becoming leader of the Parallel Society has been tough. She has fought people and monsters, experienced magic and mayhem, traveled the Earth and universes beyond. But one creature, one vile monstrosity, has been her most daunting rival - Yal-hara. Having escaped our universe to cause havoc throughout all universes, Yal-hara has now grown from a menace into a threat upon all existence.
Only Roni and the Society stand in the way. But to do that, she will need a bigger team. Much bigger. In fact, she'll need an army. Get ready. This is it. The unforgettable final book in the Parallel Society series.