Cross Server Gyms are unlocked at lvl70 together with Z-Rings and Treasure Raid. In this game mode your goal is to defend a position on each Gym in order to earn Factory Stamps which can be converted into Z-Stamps.

Z-Stamps are the material used to level up your Z-Rings.

When you defend a gym, the game attacks you trying to take your position. There are 40 waves of attacks that happen, each one with higher power than the previous one. These 40 waves of attacks lasts for around 3 days.

For each wave that you defend successfully (defeating the enemy), you will earn rewards: Factory Stamps, Gold and Exp Cards.

The amount of rewards will depend on the wave and also on the position that you're holding. Higher gym positions grand you more rewards but be careful! Only the Novice Trainer (green spot) is protected against players. Every other spot can be attacked by real players.

Once you successfully defend the 40 waves, there's no more reason to stay holding your gym position; just leave it and enter it again to restart the cycle.

Cross Server Gyms will be restarted and have their types randomized on Monday, every week.

If you need to know more about Cross Server Gyms and Z-Rings, check this video: