Halo 3 Mythic was on display at this year's PAX event. What is Halo 3 Mythic? Your guess is as good as anyone else's, but all signs point to it being a massive expansion pack for Halo 3's multiplayer.
The only details that are presently known is that the "Mythic" update is an update for the multiplayer only. It also changes the version number of Halo 3 from 1.1 (current retail with included updates) to 1.2. This information comes from AddictGaming.
Also on display at PAX were a number of additional achievements for the game. 30 new achievements made their debut at PAX, and a few details are known about them.
Killtacular: 25 GS; Picture is Killtacular medal
Aww, too bad: 25 GS; Picture is Killjoy medal
...Get the Horns: 25 GS; Picture is Bulltrue medal
Post mortem: 25 GS; Picture is Kill from the grave medal
Ghost Patrol: 25 GS; Picture is a ghost splattering someone with 3 stars behind it
Blades of Fury: 25 GS; Picture is Sword spree medal
Pull: 25 GS; Picture is Shotgun spree medal
Hammer Time: 25 GS; Picture is same as Steppin Razor except with a Gravity hammer and 5 skulls instead of 3.
Look Both Ways: 50 GS; On a Legendary Map, got a splatter spree during a ranked or social match. Splatter spree medal
Road Rage: 25 GS; Pic is Warthog splattering someone with 5 stars behind it
Flag dropped: 25 GS; Pic is two 'Killed Flag Carrier' medals, one partially covering the other
Defend this: 50 GS; On a Legendary Map, got a flag melee kill during a ranked or social match. Flag Kill medal
Came...From...Behind: On a Legendary map, got 3 assassinations on a ranked or social map. 50 GS; Assassination medal along with 3 ninja stars
Alas, Poor Yorek: 25 GS; Picture is Oddball kill medal along with 3 stars above it
Double Double: On a Legendary Map, get two double kills during a ranked or social match. 25 GS; Two double kill medals, one partially covering the other
Vidmaster Challenge: 7 on 7: 0GS; Entered into a ranked or social playlist with 7 EXP on the 7th of the month.
Vidmaster Challenge: Annual. After 9/25/08: 0GS; Completed Halo on 4-player Legendary LIVE Co-op with Iron, and everyone in Ghosts. Pic is the the skull with a hammer on the forehead in front is a green marathon symbol with 4 white stars on it
Vidmaster Challenge: Lightswitch: 0 GS; Picture is a Lieutenant symbol in front of a green marathon symbol.
Vidmaster Challenge: Brainpan: 25 GS; Picture is 6 skulls stacked into a triangle in front of green marathon symbol.[/spoil]There have been no official announcements on the "Mythic" update, nor have there been any announcements made about new achievements. A release date and additional details are not yet known.
More images on the additional achievements can be found at AddictGaming.
The only details that are presently known is that the "Mythic" update is an update for the multiplayer only. It also changes the version number of Halo 3 from 1.1 (current retail with included updates) to 1.2. This information comes from AddictGaming.
Also on display at PAX were a number of additional achievements for the game. 30 new achievements made their debut at PAX, and a few details are known about them.
Heretic Skull: 25 GS
Assembly Skull: 25 GS
Citadel Skull: 25 GS
Tank Dropper: 25 GS;
Zombie Repeller: 25 GS; Image looks like the Zombie Killing spree skull, with 2 stars behind it.
Delicious Brains: 25 GS; Picture same as ZR, except with infection spree skull.
Save this Film: 25 GS; Picture is Perfection medal.
[spoil=more achievement details]Have Fun Respawning: 25 GS; Picture is Extermination medalAssembly Skull: 25 GS
Citadel Skull: 25 GS
Tank Dropper: 25 GS;
Zombie Repeller: 25 GS; Image looks like the Zombie Killing spree skull, with 2 stars behind it.
Delicious Brains: 25 GS; Picture same as ZR, except with infection spree skull.
Save this Film: 25 GS; Picture is Perfection medal.
Killtacular: 25 GS; Picture is Killtacular medal
Aww, too bad: 25 GS; Picture is Killjoy medal
...Get the Horns: 25 GS; Picture is Bulltrue medal
Post mortem: 25 GS; Picture is Kill from the grave medal
Ghost Patrol: 25 GS; Picture is a ghost splattering someone with 3 stars behind it
Blades of Fury: 25 GS; Picture is Sword spree medal
Pull: 25 GS; Picture is Shotgun spree medal
Hammer Time: 25 GS; Picture is same as Steppin Razor except with a Gravity hammer and 5 skulls instead of 3.
Look Both Ways: 50 GS; On a Legendary Map, got a splatter spree during a ranked or social match. Splatter spree medal
Road Rage: 25 GS; Pic is Warthog splattering someone with 5 stars behind it
Flag dropped: 25 GS; Pic is two 'Killed Flag Carrier' medals, one partially covering the other
Defend this: 50 GS; On a Legendary Map, got a flag melee kill during a ranked or social match. Flag Kill medal
Came...From...Behind: On a Legendary map, got 3 assassinations on a ranked or social map. 50 GS; Assassination medal along with 3 ninja stars
Alas, Poor Yorek: 25 GS; Picture is Oddball kill medal along with 3 stars above it
Double Double: On a Legendary Map, get two double kills during a ranked or social match. 25 GS; Two double kill medals, one partially covering the other
Vidmaster Challenge: 7 on 7: 0GS; Entered into a ranked or social playlist with 7 EXP on the 7th of the month.
Vidmaster Challenge: Annual. After 9/25/08: 0GS; Completed Halo on 4-player Legendary LIVE Co-op with Iron, and everyone in Ghosts. Pic is the the skull with a hammer on the forehead in front is a green marathon symbol with 4 white stars on it
Vidmaster Challenge: Lightswitch: 0 GS; Picture is a Lieutenant symbol in front of a green marathon symbol.
Vidmaster Challenge: Brainpan: 25 GS; Picture is 6 skulls stacked into a triangle in front of green marathon symbol.[/spoil]There have been no official announcements on the "Mythic" update, nor have there been any announcements made about new achievements. A release date and additional details are not yet known.
More images on the additional achievements can be found at AddictGaming.