This isn't neccessarily true. Your introduction can still make sense without the hook, and the information inside the introduction part should really not directly depend on the hook to explain them, they should either be self explanatory, or you should explain them there.
Hopefully this helps!
In my opinion, the whole poem is quite ironic - although she is mentioning the exultation and the royal color of death, the poem itself begins with the narrator saying that she cannot breathe - that she doesn't want to die.
So, I would say that the ironic parts are:
Exultation is the going
Of an inland soul to sea, -
Past the houses, past the headlands,
Into deep eternity!
