much is of course absent ( whether rejected or merely passed over ) in the succinct account devised for the silmarillion -- where there is no mention , for example , of idril 's dream concerning meglin , the watch set on him when he went to the hills , the formation on idril 's advice of a guard bearing tuor 's emblem , the refusal of turgon to doubt the invulnerability of the city and his trust in meglin , meglin 's discovery of the secret way , *or the remarkable story that it was meglin himself who conceived the idea of the monsters of fire and iron and communicated it to melko -- a valuable defector indeed !