Aeromancer

Overview
Aeromancer is a defensive mage whose game plan is to stay out of harm's way while contesting the lane. His main wave clearing spell, Whirlwind, allows him to summon a whirlwind that damages minions over time. As soon as the whirlwind is placed, the Aeromancer can retreat to safety and simply wait for the whirlwind to clear the lane for him.

In addition, the Aeromancer can use Jet Stream to extend the reach of his basic attacks. That allows him to shoot minions from far away.

Since most mages rely on burst damage for clearing minions, Aeromancer tends to fall behind in terms of farming speed during the early-game. However, by the time mid-game hits, Whirlwind can clear a minion wave in a matter of seconds, so it can keep up with the spells of other mages.

Aeromancer is most frequently picked by defensive players who have no intention of pushing the lane during the early-game. Instead, these players focus on playing it safe during the laning phase, then make up for their passiveness by terrorizing team fights with Hurricane.

Counterplay
Hurricane is a powerful ultimate that can single-handedly decide the outcome of a team fight. However, its glaring weakness is the amount of time the Aeromancer needs for casting the spell. In that time window, the enemy can burst the Aeromancer down, or at least force him into a hopeless position.

As such, it's common to pick Electromancer as a counter to Aeromancer. When the Aeromancer starts casting Hurricane, the Electromancer has the time to respond with his own ultimate, Thunderstorm. When that happens, the Aeromancer will find himself repeatedly struck by powerful bolts and will undoubtedly die right after unleashing his ultimate, if not before then.