Vanguard

Vanguard is a Halo 3 Meta-Game Achievement. It is unlocked when the player earns 50,000 points while playing the meta-game on. This Achievement awards the player 10 Gamerpoints.

It is represented by a blue circle with a coiling dragon, the symbol for a canceled Bungie product, Phoenix. A vanguard is the foremost section in an army.

It is relatively easy to earn this achievement, due to the length of the mission, which is, according to Bungie, the longest in the entire Halo Trilogy.

Methods
On Normal, activate the Tough Luck, Famine and Thunderstorm skulls. Also, try to complete the mission in as little time as you can, as it is possible to gain a point multiplier at the end of the mission based on how much time you take to complete it.

Or if you have all the skulls you might want to try it on Heroic, with every skull but Blind, Iron, Fog, and Black Eye. Only try this if you're an experienced Halo player.

Trivia

 * This could also be an indirect allusion and reference to another designation for the Arbiter, entitled by the Prophets, "Vanguards of the Great Journey"; easily the most important aspect of this level in terms of storytelling is the Prophet of Truth's death at the Arbiter's hands.
 * A Vanguard, by definition, is a heavy battle unit, usually carrying a large sickle, scythe, or blade during battle.
 * In the Halo 3 Ultimate Guide Magazine, it is stated that you only need to earn 15,000 points to unlock this achievement, which is untrue, as you actually need 50,000 points.
 * A Vanguard is the lead group in a battle unit, battalion or strike force. The term is from the Medieval times, when it referred to the lead advancing unit, or "guard", in one's military. It is a small and elite unit, meant to strike fear into enemies, and to destroy everything in its path, leaving nothing unscathed. To be in the Vanguard was the highest honor, as it required extreme bravery and skill.

Internal

 * Halo 3 Achievements
 * The Covenant (Level)