Halo Legends

 This sweeping science-fiction saga delves into the rich Halo universe with 7 exciting stories including tales of Master Chief's mysterious origins, the Spartans' advanced combat capabilities and the tense rivalry between Spartans and Orbital Drop Shock Troopers (ODSTs).

(Source: Warnervideo.com)

1) Origins Part1 (STUDIO 4℃)
2) Origins Part2 (STUDIO 4℃)
3) The Duel (Production I.G)
4) Homecoming (Production I.G/BEETRAIN)
5) Odd One Out (Toei Animation)
6) Prototype (Bones)
7) The Babysitter (STUDIO 4℃)
8) The Package (Shinji Aramaki)

Note: Since The Package aired in two parts on Halo Waypoint and Origins has two parts the total number of episodes is 9 for the 7 stories. 5 of the 9 episodes aired online, making Halo Legends technically an ONA.