Haven was the first planet settled by the Travelers in more than 100 years.
Larrin and the Traveler fleet organized to attack the aliens. While waiting for their ships to arrive, they saved the Athosians on New Athos, who were also being attacked by the Aliens, which resulted in the Daedalus finding the Traveler fleet. Together they arrived to Haven. Colonel Caldwell had all of the planet's Travelers beamed aboard, which alerted the Aliens to their presence and started a fight between the two fleets in the planet's orbit.
Sometime later, Dr. Rodney McKay used the McKay/Zelenka Attero device on the Stargate Network, targeting the Alien's energy signature from their subspace domain. This disintegrated all traces of the Aliens, both in species and in the technology they had brought with them, across the Pegasus galaxies network. This would have wiped out any Alien's that may have remained on Haven, leaving the planet uninhabited. (SGA: "Singularity 3")