Ares was a male bat or Flier. He was one of the only bats capable of carrying a rat. He was first bonded to Henry who fell to his death in the first book after betraying the questers and joining with the rats. He is completely black- making him very hard to see in the darkness. He is described as being among the strongest of all the bats in the Underland. He was also said to have been kind of a rule-breaker so therefore liked by Henry and almost none liked ares.
In The Prophecy of Bane he rescues Gregor from two gnawers and gets angry at Gregor when he orders him around, Ares reminds Gregor that he let Henry smash to death on the rocks so that Gregor could live longer. He later goes with Gregor, Boots, Temp, Luxa, Aurora, Mareth, Andromeda, Howard, Pandora, Twitchtip, Photos Glow-Glow and Zap to find and kill the Bane. Later in the story he tells Gregor that he would always be there if he needed him and Gregor tells him if he had to choose between saving him and Boots, to save Boots first.He goes to investigate a mysterious island with Pandora, Howard's bond, searching for mites However, the mites quickly devour Pandora, stripping her to the bone, and Ares barely escapes by diving while the fish eat the mites. He later enters the rat maze with Gregor and Twitchtip, but Twitchtip collapses from fatigue while Gregor and Ares go deeper and find two rats, Goldshard and Snare, fight viciously, killing each other. Gregor finds the Bane (who turns out to be a baby) and refuses to kill it . He and Gregor take the Bane to Ripred. They fly back to Regalia to find themselves be thrown in the dungeon and put on trial along with Howard and Andromeda for treson . However, Nerissa realizes that the baby in the prophecy is the Bane not Boots and that it was good the Bane lived.
During the execution of the Prophecy of Blood in book three, he is stricken with the plague and is later found have been infected during an accident in Docter Neveeve's lab outside Regalia when he knocks over a stone jar containing the plague while his mite bites are being treated. He goes back to the Labyrinth, where he spreads the plague to the rats (although unknowingly, he didn't even know that he himself had it). He is then found by Howard and Andromeda. They then bring him to the hospital, and they get infected as well. Ares eventually gets over the plague, and flies together with Gregor again.
In the final book, Ares flies into battle with Gregor to help him fight the Bane and gets a long tear in his wing but still helps in the airlift opperation to move the nibblers from the firelands. He trains with Ajax afterwards and learns to watch his wings better. He dies later, in an attempt to give Gregor an advantage, he flies at the Bane and gets his wing caught in the Bane's mouth and gets his his neck torn open by the Bane, distracting him and letting Gregor stab him in the heart.