From the rare word “rud” meaning “red”, ruddy carries a goodly number of connotations which play together in this passage:

[12.013] and about him on all sides stretching away across the unseen floors, lay countless piles of precious things, gold wrought and unwrought, gems and jewels, and silver red-stained in the ruddy light.

“Ruddy” has to do with blushing from shame and anger, robust good health, reddish skin, heat, vigour, the reddish glow of fire, and aridity which causes flora to wither – the power, malice, and desolation of Smaug.

• 12.013 in the ruddy light.

“ruddy, adj., n., and adv.” OED Online. Oxford University Press, March 2015. Web. 1 June 2015.