The Magic: The Gathering card Bumi, Eclectic Earthbender has jumped in price from $14 to $34.70, a rise of 147% in the week since the cards were released. This card, from the MTG Jumpstart set, is eternal legal only, so we must look to the Commander format to see what has set it a'spiking.
Bumi is a mono green legendary creature that plays well with the new Avatar MTG set's earthbending mechanic. Bumi earthbends when he enters the battlefield, but more importantly, he makes all your earthbent lands stronger. Whenever Bumi himself attacks, you place two +1/+1 counters onto all your land creatures.
This makes Bumi a fantastically synergistic piece for any of the earthbending MTG commanders, all of which use green. Basically, it's a great source of buffing for all the various Tophs and other Bumi cards in the format.
In particular, Bumi, Eclectic Earthbender is getting played in about half of Toph the First Metalbender decks, and there are close to 10,000 of those logged on EDHREC. Despite all the shenanigans players came up with when that Toph was first revealed, it looks like now fans have settled on less meme-y ways of using this commander.
Looking at the best MTG cards for a Toph deck, it's all earthbending stuff rather than ludicrously broken self-exiling artifacts. You'll still play some important artifact cards, using Toph's ability to protect them, but it now seems like the repeatable earthbending is the more important part of the Toph card. In which case, it makes sense that Bumi would be a good fit for the deck.
Jumpstart cards are generally printed in lower numbers than main sets, and the way the cards and themes are distributed mean that individual rares can end up becoming very expensive. That's what looks to be happening here, as thousands of Bumis are used up in various Avatar-themed decks.
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