A Magic 2019 Core Set Elder Dragon may be to blame!
Tower Defense is a decent uncommon from Gatecrash that you can play at instant speed. It gives creatures you control +0/+5 and reach until end of turn. People have played this card before, especially in Defender decks, which are a lot of fun with Assault Formation.
But what caused this little pump spell to become a #4 best-seller on TCGPlayer in late June 2018? Enter one of the coolest Legendary Creatures in Magic 2019, Arcades, the Strategist!
Before now, Doran, the Siege Tower was the best Defender deck commander. But he's Green, White, and Black, which leaves out a lot of really sweet Defenders, such as Wall of Denial, for example. Arcades allows you to play all of those Blue Defenders, and then some!
A 4-mana 3/5 with Flying and Vigilance, this Elder Dragon draws you a card whenever a creature with defender enters the battlefield under your control. Already, this deck gains some serious card advantage. Then, there's the big effect on this card, something we've only seen before on Doran, and enchantments like Assault Formation and Rolling Stones.
"Each creature you control with defender assigns combat damage equal to its toughness rather than its power and can attack as though it didn't have defender."
There are lots of high toughness creatures in Magic with Defender. This kind of deck has been semi-competitive in the past. But Arcades, the Strategist gives you an amazing advantage by giving you really easy card draw.
So where does Tower Defense as a 2-mana instant pump spell fit in? That's because Tower Defense essentially is a +5/+5 pump spell for your team. The reach can be good sometimes, too, if you're using it defensively. But in an Arcades, the Strategist deck, you're using this combat trick more often than not on offense. But the ability to use the reach to block flyers is pretty sweet, and could swing a game in your favor.
Long story short, Tower Defense is only the first of a number of cards that should see a big boost from Arcades, the Strategist being printed. Tree of Redemption from Masters 25 is going to become quite relevant in that deck, as well as mana dorks like Axebane Guardian and Overgrown Battlement. Countless Walls and Treefolk are going to be at home in this deck, too. Plus, having access to Blue means access to crazy good spells like Cyclonic Rift, extra turn cards, and counter-magic.
While people are pretty excited that Arcades, the Strategist makes for an awesome budget Commander deck, this guy has a chance to turn Bant Defenders into an extremely competitive strategy. As a Bant lover myself, I love this guy.
And because of him, Tower Defense is going to win some games.