Complex sentence: The Six Nations council at Buffalo Creek refused to ratify the treaty, denying that their delegates had the power to give away such large tracts of land and asked the Americans for return of the deeds and promised to indemnify them for any presents they had given.
Split into simpler sentences: The Six Nations council at Buffalo Creek refused to ratify the treaty, denying that their delegates had the power to give away such large tracts of land. They asked the Americans for return of the deeds and promised to indemnify them for any presents they had given.