While I don´t like DS much, this mission is also one of the worse ones here.
My biggest issue here is the story. Garrett decides to destroy a clocktower. Because he interpreted the prophecy that way.
Oh, really? Come on, Garrett might be many things - a master thief, he can blackmail someone, or kidnap...but pure vandalism?

So, even if you go on with it, the design is not really good. Basically you climb down the tower, progressing slowly, looting and getting rid of enemies, and down there you sabotage it.
The question is: How is Garrett supposed to get out alive? It seems they haven´t thought about that. Not that the DS story is really sophisticated, but that´s even a bummer here. Garrett is usually a rather careful guy, not some fool who risks something on a whim.

Oh, and as it is DS, we have the faction system here. Regardless of your stand with the Hammerites, it will not change after that.
But surely they can forgive Garrett for destroying their clocktower and killing many brethren in the process(not to talk about people outside! Um yeah, Garrett goes full murder here?) if he has killed enough rustmites before. Right? Riiight?
Ah well, don´t think too much about it.