Wyverns are flying monsters which follow a straight-line path to the Eternia Crystals. This makes them vulnerable to correctly placed towers. Often, a map will give a warning before they start to spawn.
If a wyvern is aggroed by a hero or physical defense, they will shoot fireballs at them/it from a distance. Wyverns never aim fireballs directly at crystals; although their fireballs can still damage cores.
Wyverns can only be targeted by Ethereal Spike Traps or towers that shoot projectiles, such as Harpoon Turrets, Spider Minions, and Apprentice/Adept towers (excluding Magic Blockade). Auras and other traps can also affect wyverns within their effect radius. Players may need to build a few defenses where they can specifically deal with the them. Heroes with melee weapons can jump to hit wyverns when they get close to ground.