but you have to remember that you don't only have to takl about imaginative journeys, rather everything in general. Making a generic thesis allows you to define it with each of your text. So, what i mean is thaat start with something really bland. Articulate it in the body of your introduction with relation to your texts. That way, you connect all your text, but also focus on similar and even different (compare and contrast) ingredients asso. with a journey. Even though your focus may be imaginative (so is mine) you won't be marked down for mentioning physical and inner journeys with your essay.
so in general:
for example....
The journey leads to a greater understanding-of the character and their world. Through initiating on a journey, one undergoes an imaginary journey and inner journey of self- change, devoid of any sense of reality, and in consequence, the responder gains a greater understanding of self. This is reflected through Maragret Atwoods' poem JOURNEY TO THE INTERIOR, where her own journey into her own psyche, reveal the limitless quality of our inner self, and convey the capacity of the imaginary journey, having the power to shift one from contrasting worlds. This is also the same case for BLAH BLAH BLAH
Hope it helps. Good Luck.