A planet in the Newton System of the Kepler Verge, a human outpost.
Ontarom supports a robust biosphere. Unfortunately, said biosphere is also doomed: the orbit of Ontarom's moon Thonal has been slowly decaying since the system coalesced. Its proximity is beginning to have tidal effects, and its dynamo-like revolution through Ontarom’s magnetic field generates increasingly powerful electric storms. While some have suggested emplacement of mass effect drives in an attempt to lighten the moon and correct its orbit, the scale of such a project - tens of thousands of drives, costing enough to bankrupt the governments of all the Citadel races - make it a pipe dream. A multi-racial effort is underway to catalogue and preserve the unique genetic diversity of Ontarom’s vibrant young biosphere.
One effort was made, by a science team operating from the Systems Alliance settlement, to gather genetic data in order to determine if the highly common "Ontarom Grazers" - often known to the humans as "space cows" - were indigenous to the Ontarom ecosystem, of if they had been transplanted from elsewhere and their name thus a misnomer. The effort was abandoned when key field equipment unaccountably went missing, and the team was recalled to see to more vital tasks elsewhere.
Jokes about "shifty" space cows were made with some frequency.
The asari initially thought the humans foolish for colonizing Ontarom, but the humans had plans for the world. The communications hub they set up on the surface has hundreds of quantum communicators, whose information is spread through broadcast on the planet itself and beamed out via comm buoy. The Systems Alliance has defied the tidal disruptions and electrical storms that periodically sweep across the planet, and their facility has since grown into a crucial communications hub. Trade between the Alliance base and nearby civilian human settlements sustains planetary unity. The Alliance also trains and hires colonists to maintain the quantum communicators, further strengthening the bond.
The humans weren't in fact the first visitors, only the first to arrive in large numbers; the remains of at least one turian were discovered by Alliance personnel. It's unclear what happened to this turian. He had an ancient paper book with the Bostra Outpost insignia printed on the cover, the only clue as to his identity.
During the Reaper War, the Systems Alliance Eighth Fleet guarded Ontarom. The planet was attacked several times but the Fleet held onto the planet and its vital communications arrays. The cost of this was immense; close to half of the Eighth's ships were destroyed or damaged beyond repair and Marine units took heavy casualties, up to 60%. Bereft of its dreadnought and with the SSV Robert Oppenheimer destroyed with thousands aboard, the Eighth Fleet was restricted to hit and run attacks against Reaper forces in the Traverse.