Thine in example sentence
"No," said he, firmly persuaded of the truth of his idea (and he said it loud enough to be heard), "the greatest beauty upon earth shall not avail to make me renounce my adoration of her whom I bear stamped and graved in the core of my heart and the secret depths of my bowels; be thou, lady mine, transformed into a clumsy country wench, or into a nymph of golden Tagus weaving a web of silk and gold, let Merlin or Montesinos hold thee captive where they will; whereer thou art, thou art mine, and where'er I am, must be thine."