Ok, but what should a moon do there?
As mentioned, it influences all the alien live. Animals, creepers, but also trees. Creepers get more aggressive, animals also and they reproduce themselves. Trees reproduce, too, so if you cut too much, you destroy the forest.
Then a moon can also cause a solar eclipse. This happens, when the moon is between planet and sun, and that happens, when the moon crosses the ecliptic while pointing to the sun.
No light, no solar-energy... Nothing more has to be said...
The next are the tides. We have lakes and they have all the same level, so the are connected. And so they have tides, two times a day. Could be funny to see, how the water is coming and going. I don't think, that it should be a strategic element now (doing the Moses trick or other stuff), but maybe in future. Now I think it is just fun to see the tides. I think, the fishes might live only in the deep water. And to get better to them you can walk in the swallow water while low tide.
The last thing is the light. When full moon, the night is not completely dark. On new moon the night is most dark and a bit longer than normal. Creepers love that!
Because one moon will make everything a bit more "random" and happen more often, having two would increase that.
