Mystery is on the money...
Instead of casting Pentagram, just cast one of your creatures. You will have all the creatures you want out before Pentagram ever catches up. It's a mediocre spawnpoint in the right book, and this isn't the right book.
You need an a Crumble, an Explode, a Rust and a Disarm, probably another Dissolve/Rust/Acid Ball beyond that. I'd strongly suggest a Battleforge, Seeking Dispel, Ignite x2, Deathlink and Enfeeble in there.
First cuts I'd make would be Pentagram, Harmonise, Meditation Amulet, 1x Vampirism and Bulls Endurance.