It all feels a bit Manderly-ish to me. Anyone can trap a vanguard but only someone who absolutely hates Tywin Lannister could come up with a plan to drown an entire army.

My memory totally fails me here: are there Manderlys with him (as in, commanders)? I’m sure Big Bucket Wull [my memory makes me doubt that’s his name] has enough hatred in him for that, and more than enough will to get back big time at those who hurt the Ned’s girl (and his castle)