The Main Die is the die used for skill checks. Whenever a player rolls a skill check, the Main Die is rolled and modifiers for Skill, Stat, Equipment, and Tokens are added.
In SGS, the main die can be changed from game to game. Some games might choose to ue 1d20 to emulate the feel of D&D, while others might choose a smaller die size to change the balance.
The size of the die in comparison to the size of bonuses the characters have is a ratio that determines a lot of the feel of the game. In games with large main dice, the game will feel like luck plays more of a part than skill. In games with small dice, the game will feel like skill plays more of a part than luck.
The main die and the starting bracket determine The Ladder.