Wow, I am really falling in love with this community! You guys are the best. 
So it appears there are two possible solutions--(1) cache the response to stop repetitive API calls or (2) parse the text after the post is submitted (not while composing or editing). Am I correct in assuming that the first option will prevent a user from posting multiple cards within the same post?
@a_5mith MtG is what psychobunny said. Magic the Gathering is something invented by Wizards of the Coast--same company which developed D&D. It is a card game of good quality, and although I don't play it as much as I did in college it's a great way to spend time with friends. Also i do NOT recommend you start playing--it will absorb your money, your mind, your time, and eventually your soul.
Oh and +1 for reference to warhammer. 
@psychobunny Mox is still a viable card in the Commando/EDH tournaments. You could (probably) auction it at a decent price. Depending on the condition.
And this isn't a competition worthy plugin. MtG has too small of a niche. No, I need something more...palpable by the masses.. hmmm