Planet Relic is the first planet a new player will be sent to when they first begin playing SG. It's known as the newbie planet for this reason. The SG Divisions of the characters on planet Relic can reach only up to level 22. The units can only reach up to level 25. This limits players from getting too high, and too powerful, for newer players to handle.
It is generally recommended that users Pledge up to Morganna Prime once they are familiar enough with the game and its basics. It is recommended to do this since the most attention for the game is on Morganna Prime and if you want to reach your full potential atleast have one hero on MP