Sector 17-A of the Negative Zone.
Arthros was a barren and desolate planet created in part by the Tyannans. The Tyannans were being pulled into the Big Crunch when one of their ships crashed onto the barren planet. Having lost all their food and processors the Tyannan captain ordered the release of their life spores. Life slowly began to evolve on this planet.
It is Home to Annihilus.
Fantastic Four #140 (1973)
Arthros is located in sector 17-A of the Negative Zone. It is home planet of the tyrant Annihilus. The inhabitants of this planet were non-sentient races, which Annihilus transformed into servitor/Scavengers, insectivorids by using the Tyannans spores of life. The other known inhabitants of Arthos are Eradica, Extermina, Extirpia, Lord Hawal, and Admiral Salo.