Strategeist

Strategeist is a grand strategy game in which you take on the mantle of a national spirit and guide a nation through time to build an empire and secure your place in history. Starting in the year 1206, at the beginning of the Mongol Invasions, you will pick one of over a thousand countries and attempt to forge a new destiny by making strategic decisions about diplomacy, technology, economy, internal politics, and war.

https://store.steampowered.com/app/662440/Strategeist

The Invitation link
You can contribute to this Play Session creating your own playtesting video recording:
Start a playtesting video recording

The reward for the Playtester

Retail copy of the game upon release