Figurative Language is the stylistic technique employed here.
Explanation:
The poem given here is good example of figurative language as there are many events that are directly or indirectly compared to one another and thus bound seamlessly together to make a beautiful image journey through the lines.
The figurative use of the word wardrobe to open a new world for the person and then their use of imagery to describe their new surroundings is one of the rime and the most clear examples here of that happening.
