Siege-Gang Commander This is one of the best creatures from MTGs past (well into 2011, I dare say), and it doesnt hold a candle to actual creatures
It is meant to both be drafted and provide cards for Historic, but does not contain every card in both of those sets
You can play Norman Osborn early, build up some counters with connive, then transform it into a beefy, evasive Green Goblin
Awaken the Maelstrom Baleful Mastery Black Widow, Agile Avenger Booby Trap Consecrated Sphinx Defacing Duskmage Faerie Mastermind Fate Unraveler Gleaming Splendor Infernal Offering Kederekt Parasite Leela, Sevateem Warrior Malignant Growth Mathas, Fiend Seeker Mind's Eye Mind's Eye Nekusar, the Mindrazer Norn's Decree North Pole Research Base Notion Thief Ob Nixilis Reignited Ob Nixilis, the Hate-Twisted Orcish Bowmasters Pendant of Prosperity Razorkin Needlehead Red Death, Shipwrecker Saltwater Stalwart Sapphire Charm Sazacap's Brew Scrawling Crawler Sheoldred, the Apocalypse Smothering Tithe Tataru Taru The Unagi of Kyoshi Island Thief of Existence Trouble in Pairs Underworld Dreams Wedding Ring Xyris, the Writhing Storm Zurzoth, Chaos Rider
Your opponent will likely have a few stronger creatures by this point, and when they attack through it, they can still do a good chunk of damage to Jace
Casting a spell that's a creature and also another type (such as an artifact creature) is still casting a creature spell, so prowess won't trigger in that case either