The entire first blood.

[Anonymoose]

Since I can't find the phrase "first blood" in Heavensward content, I'm going to guess you meant "first brood".

The First Brood refers to Midgardsormr's children - the seven great wyrms seen with him on the artwork. I'm going to avoid spoilers since most of the relevant information is gained after your encounter with Tioman. But suffice to say they flew to corners of the world and gave birth to enormous broods of dragons - all the dragons of the world are descended from these seven, as far as we've been told.

Midgardsormr is thus considered the Progenitor - the Father of Dragons.

The names and bare bones information are follows, in no particular order but convenience.

Bahamut
Flew to Meracydia, fathered a great brood alongside Tiamat.
Slain by Allag and resurrected as a primal shade.

Tiamat
Flew to Meracydia, mothered a great brood alongside Bahamut.
You'll meet her later.

Ratatoskr
Stayed in Eorzea. Deceased as of the beginning of the game.
You'll hear more about her later.

Hraesvelgr
Stayed in Eorzea.
You'll hear more about him pretty much right now.

Nidhogg
Stayed in Eorzea. Presently waging a 1,000 year war on Ishgard.
Major antagonist of Heavensward.

UNKNOWN
The sixth Celestial Dragon is named and has a history. It will not be revealed until later.

UNKNOWN
The seventh Celestial Dragon is named and has a history. It will not be revealed until later.



BONUS INFORMATION
Dragons reproduce asexually, which explains Midgardsormr being a single father.
Dragon mates are lifelong spiritual connections, not reproductive ones, which makes Bahamut/Tiamat a little easier to understand.
Tioman is an old and powerful dragon, but not from among the first brood.