Pre Halo CE Attack on Reach, Arbiter pursues Pillar of Autumn to Installation 04 but gets there first because the Covenant are always faster.

Halo CE Arbiter loses the ring, goes home in disgrace.

Pre Halo 2 The Heretic steps up in his campaign (possibly influences Vergil?) Arbiter is made Arbiter.

Halo 2 Arbiter kills Heretic. Returns to High Charity.

Regret goes to Earth.

ODST Vergil defects.

Halo 2/ODST Regret jumps away.

Immediately after to this or just prior to this, he gives the order for the Elites left on Earth to be killed.

ODST Vergil holes up in the SI and patches him up.

Halo 2 Regret gets killed. High Charity jumps to the Delta Halo position.

ODST Vergil rescued, defects to human side.

Halo 2 With Regret's death, Truth replaces the Elite honour guard, sends Arbiter and Half-Jaw on separate suicide missions. Both survive.

Arbiter meets Gravemind, finds the captured Councillors and joins up with Johnson and Miranda.

ODST Upon return, Johnson gets some information out of Vergil. Presumably using post coital cigars if the aliens like line is anything to go by.

Halo 3 Elites join humans for last hurrah.