On a black jade altar lay Yasmela

The army of Thugra Khotan has been defeated and has fled the battlefield taking Princess Yasmela with his. CONAN finds them both in an ancient ruin.

On a black jade altar lay Yasmela, her naked body gleaming like ivory in the weird light. Her garments lay strewn on the floor, as if ripped from her in brutal haste.

From "Black Colossus"
Page 132. The Complete Chronicles of CONAN.

I've found a few examples of pale women of dark altars... they were probably all "supple" as well, a few more to follow.

Naked girls and altars...

After the near extinction of the two peoples battling within the ancient city of Xuchotl, Valeria is taken prisoner by an evil witch who wants to sacrifice her and drain her vitality to sustain her own youth.

On the altar lay Valeria, stark naked, her white flesh gleaming in shocking contrast to the glistening ebon stone. She was not bound. She lay at full length, her arms stretched out above her head to their fullest extent. At the head of the altar knelt a young man, holding her wrists firmly. A young woman knelt at the other end of the altar, grasping her ankles. Between them she could neither rise nor move.

From "Red Nails"
Page 569. The Complete Chronicles of CONAN.