Princess

Location Castles
To free a Princess, you first have to kill the castle Jester, who drops a key. The key opens one of the two cells, so you may not be able to free the Princess if you're not lucky. Once you open the cell, the Princess will follow you. Bring her to the castle entrance to finish the rescue.

After a successful rescue, the Princess will give you 3,000 Hit Points, 3,000 Gold, and 3,000 Experience. If you're Level 8 and a space ace, she will also tell you where to find the Time Machine, which spawns in the northwest area of the current Continent.
Compare Princess to other Creatures
Jester Merchant

Related

Lands of the Dark Unknown

Page 4
Obtain the Blue Gem from the King in The Black Dragons Castle.

Adventures in Space

Page 5
Obtain a Shuttle and become a Space Ace by destroying 20 enemy vessels, locating a Time Machine in the process.

Princess

Location Castles
HP 1
To free a Princess, you first have to kill the castle Jester, who drops a key. The key opens one of the two cells, so you may not be able to free the Princess if you're not lucky. Once you open the cell, the Princess will follow you. Bring her to the castle entrance to finish the rescue.

After a successful rescue, the Princess will give you 500 Hit Points, 500 pence, and 500 Experience. If you're a space ace, she will also tell you where to find the Time Machine, which spawns in the northwest area of the current Continent.