The fourth boss level in HTFA 5. It takes place deep inside a cave in Jungle Kingdom. The boss is Fire Dragon, which rises from the lava there and can attack by shooting flame.
While there's lava in the level, there are some solid ground and bridges above it. The Fire Dragon, however, can simply pass through those as it rises from and sinks into lava whenever it wants to change its position, which can be either on the right side, the left side, or at the center. Much like The Red Dragon from the previous kingdom, its flame's range isn't really long, but it can easily damage you if Fire Dragon is on the center of the level. To help you, there are four Heart items, with two of them on the left side while the other two are on the right side. There are five small floating platforms above the ground, with the central platform holding an extra life. Beware of the two Podoboos, though.
To defeat it, you simply have to shoot the boss enough times. Defeating Fire Dragon will grant you access to the next kingdom, Ice Kingdom.