When Aunt is dead, her terrified hands will lie Still ringed with ordeals she was mastered by. (9-10)
Here, the speaker imagines that Aunt J is dead, even though she's actually still alive. (Creepy, right?) She imagines that, even in death, Aunt J will be terrified; it's like there's no way for her to escape the ordeals and horrors of her life. (Double creepy.)
The tigers in the panel that she made Will go on prancing, proud and unafraid. (11-12)
Even though the speaker imagines that her aunt is dead, she imagines that the tigers will still be "prancing." Aunt J is forever terrified, and the tigers are forever "prancing"—active, upbeat, even joyful! A good deal for the tigers, anyway. Still, Aunt J may die, but her creations will remain after her death. They'll be "proud and unafraid"—and they'll live forever in art.