We usually think of the mythological Helen as a beautiful and vibrant young woman, but in H.D.'s work, she's deathly still. As the poem progresses, she seems increasingly like a stone or marble statue of a woman, rather than a real, live lady. And when the poem anticipates Helen's death in its last stanza, it almost seems expected. Helen is so devoid of life throughout the poem that the image of her body-turned-to-ash is not even all that surprising.
Line 2: The first description of Helen is of her "still eyes." Eyes are rarely still; they're constantly looking around, taking things in. But Helen's eyes are still, and it makes her seem statuesque.
Line 4: Here, Helen is standing still. Again, no movement. Just stagnation.
Line 12: Now it is Greece that is "unmoved" by Helen. She is still, and she is unable to stir the hearts of her countrymen. She is powerless to "move" them.
Lines 16-18: In the last lines of the poem, we're faced with the ultimate stillness: the image of Helen's cremated body at her funeral. It doesn't get more still than death.