Ratocalypse is a Fire Emblem-style auto battler about zombie rats from the Ratopia devs

Cassel Games — the studio behind Ratopia — has announced Ratocalypse, a strategy RPG auto battler set in a medieval kingdom of anthropomorphic rats wiped out by a zombie plague. No release date or window yet, but a demo is already live on Steam with several hours of content.

The core hook is programmable unit AI. Before battles, you build behaviour chains for each unit by slotting skills into a priority list — setting activation conditions like HP thresholds or unit counts on the field, choosing targets, and ordering skills to fire before or after others. Once the fight starts, your units run those routines on their own, though you can still intervene with a handful of active abilities mid-battle. Units die easily, so that intervention matters. The overarching goal is to uncover what caused the plague and, ideally, cure it.

Cassel Games released Ratopia — a Terraria-style city builder with rats — last year, and the game received an update as recently as this July. Ratocalypse looks like a deliberate genre pivot: where Ratopia leaned into base-building and survival, Ratocalypse is squarely in tactical RPG territory, drawing comparisons to Fire Emblem in its unit-focused, turn-adjacent structure.

There's no launch window to pin down yet, but the Steam demo is available now if you want to test the AI-building system before committing to a wishlist.