Costing four mana to cast, and two more for this artifact's activated ability, Monster Manual allows you to play a creature from your hand directly into play in an effect reminescent of the popular Commander card Elvish Piper
Not only are they great to safely, securely store cards, but they also provide easy visibility and access for players when putting together their decks
That doesnt seem like a big hurdle, but it seems more likely that Francisco will be played as a combo enabler than an aggro beater
8 mana for a 6/6 flyer isn't the best costing, but the exile clause can be really powerful
Legendary Creature - Human Shaman Color tag templates(None) Legion Warboss Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.) At the beginning of combat on your turn, create a 1/1 red Goblin creature token
But prowess decks have a more ephemeral strategy, and those cards become a lot better here