Population: 13.5 million (all pop. estimates are pre-invasion)
Altakiril is a garden world on the outer edge of its stars habitable zone. The planet is largely frozen, yet it features native dextro-amino-acid-based life in its lower latitudes. These species evolved to withstand periodic freezing and compensate for the cold with spectacular population explosions during the long, mild summers.
Hardy, independent-minded turians colonized the planet. The quarians briefly considered contesting them but were daunted by the virulence of the planet's infectious life during the growing season, not to mention the colonists who had tied to warlords elsewhere in the Shrike Abyssal.
Altakiril's citizens were wiped out by Reapers bombardment despite the planet having a reasonably high population, which would usually make it a candidate for harvesting. Allied intelligence suggests that the colonists kept anti-space weaponry in population centers, so the Reapers limited their risk by destroying the threat and moving on.