Age of Mythology: Retold

This is an easy achievement.

Start a skirmish with the Greeks using Zeus
Settings:

• Standard Mode
• Game Speed Fast
• Infinite resources
• Reveal all
• 1v1

Start:

1. For this you will need to do it across 5 matches, it's not possible to get in a single match.
2. Begin by building the temple and then upgrade to age 2, select any god.
3. Build the armory and then upgrade to age 3, select any god.
4. Finally build 10 Fortresses which is the max limit per game.
5. Once complete start a new game and repeat this until you've built another 10 Fortresses. Do this 5 times and you should total 50 Fortresses across 5 matches which will earn this achievement.

If you need more help with this you can follow my video guide below which will begin at this achievement:

You should get this during your pursuit of other achievements.

If you want to rush this specific achievement (for a challenge f.e.), do the following:

Start a skirmish with one AI on lowest difficulty. Set ressources to infinite. If you are comfortable with it, increase the games speed. God doesn't really matter.
Once the game starts auto-queue villagers, build a temple, advance an age. While the age goes up, built houses.
Once in the next age, built a forge, advance once again.
In the third age you can start building fortresses. Use all your villagers to built ten anywhere. Best if you can fit them all on one screen.
You can have ten of these max at any one point. So delete them and then built another ten. Repeat until cheevo.

The AI won't attack, so you do not need to worry.