Sizzling Summer Series - meet King Arthur's daughter by Katherine Roberts
King Arthur's daughter... Rhianna Pendragon
This series for young readers begins with a famous sword named Excalibur, which according to legend was thrown into a lake at King Arthur's request while he lies dying of wounds gained in battle against his evil nephew Mordred. It would have been a lot easier if he'd told his knights to keep the sword safe for his daughter Rhianna, but she's hiding in Fairyland and they aren't supposed to know anything about her. Besides, if they just gave her the sword there wouldn't be much of a story, and then we wouldn't get to meet Nimue, mermaid of the lake (who is not quite as sweet as you might think).
Mordred, crippled in the duel with Arthur and plotting his revenge, soon finds out where the girl is hiding and is determined to stop Rhianna returning to Camelot to claim her father's throne. Aided from beyond the grave by his witch-mother Morgan Le Fay, he sets out to destroy Camelot's rightful heiress and the kingdom she defends.
Fortunately, Rhianna (having grown up in Fairyland) has a few tricks up her armoured sleeve - a fairy horse called Alba with the power to mist through solid objects, and her faithful friend Prince Elphin who plays an enchanted harp with his six-fingered hands. They are joined on their quest by fumbling but eager squire Cai, and troubled maid Arianrhod who used to serve Morgan Le Fay. Against the advice of King Arthur's knights, the four friends set out to seek his Sword, Lance, Crown, and finally the elusive Grail that has the power to bring the king back from the dead... or does it?