The Lava Hound is the earliest available legendary card you can get since it is unlocked in Arena 4. The Lava Hound is a flying tank troop that only targets buildings/towers and splits into 6 Lava Pups after death. It has a very large health with low damage and slow movement and attack speed. However once it splits into Lava Pups, each Lava Pups will have low health and higher damage than its original form as a Lava Hound.
Since there are only few cards that can damage flying units, having a Lava Hound in early Arenas is hard to counter. However in higher Arenas, the Lava Hound’s biggest weakness is the Inferno Tower. Ideally, having a swarm troop together with the Lava Hound is a great combination against the Inferno Tower.