Much like Conjurer's Closet, you'll find Panharmonicon enables silly combos that provide infinite mana, turns, life, or whatever else you can think of thanks to duplicate enters-the-battlefield triggers
While he was a part of the ultimately unsuccessful attempt to use the Filigree Sylex on New Phyrexia, Tytvar acquitted himself well on the mission, taking down Tibalt in single combat while protecting and rallying his planeswalker allies even in the face of what seemed like near-certain defeat
This, for a card from 2013's Team Plasma box, which at the time retailed for 20 bucks
You lose life equal to that permanents mana value
It gives a great stat boost to a creature at instant speed, which can be helpful if that creature is also your Ring-bearer