what were The Silent Watchers?

[Lord Halsar]

Originally Posted by The Saucepan Man

From The Tower of Cirith Ungol:This suggests that they were, in physical form, statues, but that they were imbued with some kind of spirit. And since the spirits inside them are said to have been evil, it seems likely that they (the spirits) were placed there by Sauron, rather than by the Men of Gondor who built the Tower.

You have a point about that. but i have another theory. what if Sauron tainted the spirits of the blue wizards and used their spirits in the watchers?
so little is known of the blue wizards, it could be possible