The Lava Hound is a somewhat fast, low-damage aerial tank with a high hitpoint. Level 6 of Dark Barracks is where it is unlocked.
Strategy
Offensive: Lava Hounds are basically the air version of the golem, and they have a high health. The same way that golems can defend a group of wizards or witches, they can also be deployed to protect dragons, minions, healers, and balloons. They cause little damage on their own and nearly always need assistance from someone else, so they may be easily occupied while other soldiers annihilate the base thanks to their priority versus air defenses.
Defensive: It makes sense to disperse your air defenses. This increases the effectiveness of Air Bombs and Wizard Towers by forcing attackers to position their Air Troops for safety close to the Lava Hounds. In order to increase the likelihood that Lava Hounds will activate your air defenses, place Seeking Air Mines nearby to them as well. For level 5 Clan Castle or above, Lava Hounds make an excellent troop, especially in higher leagues.