The longer letter from Grepolis

Grepolis starts you with a single city on a single island and a choice of god, and then grows in two directions at once: outward across the sea, where every island has villages to farm and rivals to watch, and upward through the gods, whose favour buys mythical units and spells that can turn a fight. Athena's owl and Poseidon's hydra sound like flavour. They aren't.

Worlds end. Alliances race to build and hold World Wonders, and when that's done the server closes and the survivors move on to a new one. It gives the game a seasonal urgency the builders don't have, and it means a newcomer can pick a fresh world and be nobody's easy target for a while. Join one that's less than two weeks old; beginner protection is generous but it doesn't help if everyone around you is three months in.

The weather is the warning. Gold buys advisors, speed and a lot of convenience, and on a competitive world a non-paying player feels it by the second month. It's still very playable without spending; it's just louder about the shop than the two cards above it on the rack.