Games like Fragmentum
Games like Fragmentum include Castle Story, From the Depths, Planetary Annihilation: TITANS, 8-Bit Armies, and Age of Empires II (Retired). We matched them by the tags players give Fragmentum on Steam (Strategy, Indie, Building, RTS, and Voxel): closest matches first, and among equally close ones the better-known games.

Castle Story
Shared: Strategy · Building · Indie

From the Depths
Shared: Building · RTS · Strategy

Planetary Annihilation: TITANS
Shared: Strategy · RTS · Multiplayer

8-Bit Armies
Shared: Strategy · Indie · RTS

Age of Empires II (Retired)
Shared: Strategy · RTS · Multiplayer

Dota 2
Shared: Strategy · Multiplayer · RTS

Buckshot Roulette
Shared: Strategy · Multiplayer · Indie

Teardown
Shared: Voxel · Indie · Multiplayer

Rusted Warfare - RTS
Shared: Strategy · RTS · Indie

8-Bit Hordes
Shared: Strategy · Indie · RTS

Company of Heroes 2
Shared: Strategy · RTS · Multiplayer

7 Days to Die
Shared: Multiplayer · Building · Voxel

Mindustry
Shared: Strategy · RTS · Building

Plague Inc: Evolved
Shared: Strategy · Indie · Multiplayer

Natural Selection 2
Shared: Strategy · Multiplayer · RTS

Circle Empires
Shared: Strategy · Indie · RTS

Farthest Frontier
Shared: Strategy · Building · RTS

Wargame: Red Dragon
Shared: Strategy · RTS · Multiplayer

Tooth and Tail
Shared: Strategy · Indie · RTS

Total War: WARHAMMER II
Shared: Strategy · RTS · Multiplayer

Town of Salem
Shared: Strategy · Indie · Multiplayer

Rise of Nations: Extended Edition
Shared: Strategy · RTS · Multiplayer

Command & Conquer™ Remastered Collection
Shared: Strategy · RTS · Multiplayer

Age of Empires III: Definitive Edition
Shared: Strategy · RTS · Multiplayer