Short answers, pulled from the story.
The Cherokee Nation, Choctaw, and Creek signed treaties with the Confederacy under pressure from slave-holding factions. The Eastern Band Cherokee formed Thomas Legion while the Catawba enlisted in South Carolina Volunteer Infantry regiments.
The Delaware Nation formally declared for the Union on the 1st of October 1861. One hundred seventy of 201 able-bodied Delaware men subsequently enlisted in the Union Army to fight against Confederate forces.
Company K fought their final engagement at the Battle of the Crater on the 30th of July 1864 where they were cut off and low on ammunition. They chanted a death song and died together in a group after being mortally wounded during the massive underground explosion intended to breach Confederate lines.
Colonel John Chivington led a dawn assault on the peaceful encampment near Big Sandy Creek on the 29th of November 1864. Estimates place the dead between 160 and 200 unarmed women and children during this attack authorized by Colorado Territory Governor John Evans.
Native Americans remained classified as domestic dependent nations and were excluded from full citizenship rights under the Fourteenth Amendment. The amendment continued to exclude Indians not taxed from legal protections granted to formerly enslaved people through Reconstruction Amendments.