Could be the League has learned of the watchers and is using the Abyss as a staging grounds of containment for them. Of course, that would mean that Lissandra's job of hiding their existance was poorly done (or that the Institute violated its rule of "not acting of what they see in a Champion's mind", she doesn't need a barganing chip for that, it's a part of their rules) and I don't think that is the case.
Most likely, the League is taking steps towards making sure that the Freljord conflict doesn't become a Rune War-level event. The first step towards that would be aquiring the land for field of justice in that area, to make sure the League has a slight grip on the area and a little pull as a result, and the next would then be to actually work towards solving the conflict with battles on the Field of Justice.
Of course, this conflict in itself isn't simple to solve inherantly because of how many players it has. This isn't Noxus vs. Demacia, this is Lissandra vs. Ashe vs. Sejuani, and the 1v1v1 style ALWAYS complicates matters.