A sarcophagus was a large stone coffin. It protected the mummified body from decaying for as long as possible. Look closely at what this pharaoh is holding.
He is carrying two amulets to help him in the afterlife: the djed pillar (this has lines on it) and the ankh (which has a loop at the top). The djed pillar could give someone strength in the afterlife; the ankh gave eternal life.
See if you can find these amulets when you visit Room 63.