Great! Let's have her either with Rathakku's forest forces, waiting to attack newcomers, or choose a tower (ideally not the one Sarah serves) that River can help scale to further the attacks. She can pretend to still have Alem loyalties, if you want. Mostly, the key difference is - she isn't "default cartoon villain evil" when Clawed, but death lords control their units by giving them a very narrow, singular objective. So she will be hyperfocused on whatever you decide her task to be and also legit petrified of Alem forces and willing to take them down because they are attacking her people.