Break through
Sam is bathing himself in the flames.
He discovered this ability to use direct flames for his consumption through a guess. He is just disintegrating the flames using his manipulating ability and using the absorption ability to make it his.
After all, the fire is also essentially a form of spiritual energy and the fire doesn't have many components in and itself. So, it is easy for him to do so.
But will any firework for him in this way? In a sense, yes, but the burning object which acts as fuel should consist of more spiritual energy to be able to have any actual benefit for Sam.
The whole banyan expanse and the beasts within it including the parasite consists of a high amount of spiritual energy which is going to be burnt into the flames and becomes Sam's food.
As he was busy devouring the flames, someone else other than Sam's group are approaching them after seeing the huge flames and smoke.