It's been a long time since I played EA Arco, but in a recent game I'm playing them and I thought I might pick up a quick province by seducing the lowly Druid commanding some woodsmen in a forest.
I'm not sure if I didn't notice the Dark Vines, or just didn't think about them, but instead of getting a single N1H1 commander, I ended up with a N1B2, and he even brought along his retinue of 18 slaves.
I think I'll head back for the other 4 druids

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EA Arco has a pretty quick route to blood magic if you can manage to find an indy province with Dark Vines in it!