They Are Billions

Verdict

The final wave of a They Are Billions survival map is the single most frightening thing in the genre: a wall of infected that fills the horizon and tests every wall, ballista and shocking tower you placed over the previous hundred days. Before that it is a colony builder with real tension, because one zombie through a gap infects a house, and a house infects a street.

The New Empire campaign added at the full release is long and generous, with hero missions and a research tree that unlocks across it. Pausing is allowed at any time, and you will use it. It is unforgiving, the save system is deliberately a single file, and it is still, six years on, the standard for this kind of defence.

Towers 16 of 20

Wooden walls, stone walls, gates, ballistas, shocking towers, executors and a small roster of soldiers, snipers and Thanatos launchers you steer yourself. Each piece has a clear role; there are simply not many pieces, and the research order is mostly fixed.

Lanes 17 of 20

Procedurally generated survival maps across six biomes with choke points you must find rather than be shown, plus hand-built campaign missions. Reading the terrain in the first ten minutes decides the next four hours.

Waves 19 of 20

The pressure is the point: steady wandering infected, then timed swarms that grow until the final one. Every warning is honest and every breach is your fault, which is exactly how it should feel. The curve on the campaign is steep enough to lose people in the first few missions.

Economy 18 of 20

Gold, wood, stone, iron, oil, workers, food and energy, all balanced against the need to expand into dangerous ground. The best economy on the list for how much it rewards planning and punishes greed.

Longevity 15 of 20

A long campaign and endless survival maps with a seed system, but no co-op, no Workshop and no new content since 2020. What is here is deep; it will not grow.

In pictures

Report written against the Steam build current on 31 October 2026; prices read the same day.