You can unlock it in the P.E.K.K.A.’s Playhouse (Arena 4)
High damage capability.
Single target defensive building.
Inferno Tower is great against high hitpoint troops like a Giants, Golems or Ballons.
If you want to destroy this tower you must swarm it with low Elixir units. You can use Skeletons or Spear Goblins. They will outnumber the tower and destroy it.
To protect the tower before swarm attack put in to the battlefield area damage card. Bomb Tower, Baby Dragon, Valkyrie or Bomber.