Harnfel, Horn of Abundance is a five-mana card filtering engine
Since youre bringing back a Goblin to your hand each turn, you can keep bringing back a card with either an enter the battlefield effect like Siege-Gang Commander or constantly have a creature to sacrifice to another effect
At six mana (three colorless, one each blue, black, and red), he's a little more expensive than other Commanders you're likely to encounter, but he brings excellent value and staying power to your battlefield
Also, her ability obviously hints at you getting rid of her hexproof to kill a pesky artifact or enchantment, but it doesnt say it has to be that type of counter
Theyre often focused on using tons of mana-producing creatures like Heritage Druid and Priest of Titania to generate a massive amount of mana
Useful for creating your own cards games or for creating proxies for trading game cards that are too valuable to actually play with