Complex sentence: The territories of Green and Black dragons frequently overlap, but as greens are more powerful, they typically hold the upper hand, but most Greens will allow a Black dragon to remain in their forest, so long as the lesser dragon remains in the swamps.
Split into simpler sentences: The territories of Green and Black dragons frequently overlap, but as greens are more powerful, they typically hold the upper hand. Greens may allow a Black dragon to remain in their forest, as long as the lesser dragon remains in the swamps.