This would be called Lego Prydain. the Books are by Lloyd Alexanda.
The names of the people are in the order of the people.
The first few are baddies.
baddies:
Arwen ( he can turn into anything), deathless men, the horned king and archren ( she is a baddie on the first three, but becomes a good at the end of the third one).
Goodies
Coll, Gwydion, Dallben (he's a wizard), Gurgi (a creature), Elenwy, Taran worrior, Taran farmer, Flam Ffleudur, Doli and Gwiniff.
Animals:
Arwen (he changes into a snake at one point), the grwffiws (these are big enemy birds, I would surgest to make them look like the old quididatrols only black), Hen-Wen (a pig), Caw (a crow) and lyan (he's really a huge cat the same size as a house).
The picture at the top is also important, this is the cave of Dallben. This is the number 1 set I would like Lego to make. This would come with Dallben, Taran worrior, Call, Gwydian, Flame Ffleudur, Guigi and Elenwy.
Most people like medivel places as well