Tarn

Tarn is the ground-power counterweight to Vos in the pre-war city-state system, and its published history gives it a ruler who matters: Shockwave, described as a military dictator of Tarn before the Great War. That single detail reframes Shockwave from a loyal lieutenant into a head of state who chose to serve Megatron, which is a large part of why the character reads so differently in the comics than in the cartoon.

Tarn's rivalry with Vos over Cybertron's dwindling energy supplies escalated until both cities launched photon missiles at the same instant. Both were destroyed. The event functions in G1 backstory as the point of no return: the old order of competing polities incinerated itself, the survivors radicalised, and the resulting vacuum was filled by two ideological armies rather than a dozen governments.

Tarn later became one of the most reused names in the franchise, most famously as the alias of the Decepticon Justice Division's leader in IDW's comics, which has largely eclipsed the original city in search results. For G1 the city is a Marvel-era reference-book entity with no cartoon presence, valuable mainly for what it establishes about Shockwave and about how Cybertron's politics collapsed.

• Shockwave's dictatorship of Tarn is the single most consequential piece of Cybertronian political backstory Marvel published, and it never appears in the cartoon.
• IDW later named a Decepticon character Tarn after the city, and that character now dominates any search for the name.
• Tarn and Vos are always cited together; no G1 source describes either city's culture or appearance in any detail.
• The city is listed alongside Iacon as one of the key three powers, making it politically the equal of the Autobot capital.