Halo 3: ODST expansion pack features an excellent cooperative mode called Firefight. But you need to complete certain important missions to unlock Firefight missions and characters. Find out how to unlock Firefight missions, characters and Halo 3 Recon armor in this Halo 3: ODST achievements guide.
Halo 3: ODST: What's New?
A prelude to Halo 3, Halo 3: ODST expansion pack neither features Master Chief nor his advance armor or reflexes. But, it does feature an advanced VISR, or Visual Intelligence System Reconnaissance, which performs a number of functions, including highlighting nearby objects of importance and hostile units. (For an overview of the VISR refer to our Halo 3: ODST Basic Combat Training Guide.)
Besides the unique HUD, Halo 3: ODST features an excellent detective story-like plot. The new open-ended Mombasa city map has plenty of objects and weapons to access. The exclusive weapons also include ones seen in the initial Halo video game. ODST also features an immersive cooperative gameplay mode called Firefight. The game can be played cooperatively with three more players on Xbox Live. The Firefight mode also contains Halo 3 ODST skulls to add some intensity and variation in gameplay. Moreover, players can also unlock Firefight missions and characters by completing certain missions in single player campaigns. Some Halo 3: ODST achievements can be unlocked by finishing certain Firefight missions.
Halo 3: ODST Achievements and Unlockables
There are plenty of unlockables and achievements on Halo 3: ODST. Players can also unlock the exclusive Halo 3: ODST Recon Armor by unbolting certain Halo 3 and ODST achievements. Other unlockables include the Firefight missions, characters and armor. These Halo 3: ODST achievements might be difficult or easy to achieve, but the end result will be rewarding for all Halo fanatics.
How to Unlock Firefight Missions in ODST?
Lost Platoon: Finish campaign mission 3 (Uplift Reserve) on any difficulty level.
Alpha Site: The ONI Alpha Site (campaign mission 5) has to be completed successfully on any difficulty mode to unlock this Fire fight mission.
Chasm Ten: Finish Campaign Mission 8 (Date Hive Campaign) to unlock this Firefight Map. You can unlock it at any difficulty level.
Last Exit: Finish Campaign Mission 9 (Coastal Highway Campaign) on any difficulty mode to unlock the Last Exit map.
How to Unlock Firefight Mission Characters?
To unlock Buck, finish mission 2 on any difficulty mode
To unlock Mickey, finish mission 4 on any difficulty level
To unlock Dare, finish the campaign mode on Legendary difficulty mode
To unlock Dutch, finish campaign mission 3 on any difficulty level.
You cannot unlock UNSC Sergeant Avery Johnson by completing any missions. The unlock codes were provided to users who pre-ordered the ODST expansion pack.
Unlocking the Halo 3 ODST Recon Armor
Now you can unlock the Recon Armor yourself, thanks to ODST. All you have to do is unlock three Halo 3 ODST achievements as well as four achievements in the parent game (Halo 3). Here are achievements for both original and its expansion pack:
Three Halo ODST Achievements: Vidmaster Challenge Achievements
Classic: Complete any level alone on Legendary difficulty level. But make sure you are signed in to Xbox LIVE. You also have to complete the level without any grenade thrown or shots fired.
Endure: In Firefight Co-op mode, get past the fourth set. Make sure you play it in Heroic difficulty level on Xbox Live 4 player Co-op mode.
Déjà vu: Finish the Coastal Highway mission on Legendary difficulty level. You will have to sign in to Xbox Live and play on 4-player co-operative mode. You will also have to activate the Iron Skull. Do not use the Scorpion tank or Warthog.
Four Halo 3 Achievements: Vidmaster Challenges
Annual: Finish Halo 3 on Legendary difficulty level. You must be signed in to LIVE and have the Iron Skull Activated. Make sure you are on a 4 player Co-op mode and all players must possess Ghosts, a special Type-32 rapid assault vehicle in Halo 3.
Lightswitch: Achieve the Lieutenant rank in any playlist in the new progression system (EXP)
Brainpan: The Mythic maps contain some hidden skulls. Find all and unlock this achievement. 
7 On 7: You have to enter a rank playlist or a social playlist. You will also have to earn 7 EXP on the seventh date of any month. This is quite unique achievement as it relies on a specific date. You will have to sign in to Xbox Live in on the 7th of any month. Make sure you earn 7 EXP before the seventh date of any month to easily achieve this Halo 3 achievement.
After you complete all three Halo 3 ODST Achievements as well as 4 Halo 3 achievements, acquire the unlock code at Bungie.net to unlock the Halo 3 ODST Recon Armor.