(someone) is descended from (someone)

Use this phrase to explain who someone's ancestors were. Your ancestors are the people like your great-great-grandparents, great-great-great-grandparents, and so on.

You can say that a person "is descended from" a single person:

She claims to be descended from Abraham Lincoln.

Or you can say that someone is descended from a group of people:

They're descended from the original inhabitants of the island.

a (first/second/19th/etc.)-century (something)

When English speakers say "20th century", it means the years from 1901-2000. Similarly, "18th century" is 1701-1800, and "first centry" is 1-100 A.D.

You can use this phrase as an adjective like this:

They discovered the sunken remains of a fifteenth-century trading ship.

They didn't have our modern 21st-century conveniences back then.

Without the hyphen ("-"), you can use this phrase as a noun too:

They've been fighting off and on since the 17th century.

a warrior

A "warrior" is someone who fights in battles.

We mostly use the word "warrior" to talk about people from the past who fought hand-to-hand, using things like swords, bows and arrows, and spears. Warriors were not only strong, but also a little wild.

You could also call a modern soldier a "warrior". In that case, it would sound like that soldier was very strong, brave, and determined.