Hey,
Yep! You are correct. Those 3 cards define the shape, vertices, and lines. The other features are decorative elements you add on to the spell from other cards or, when you complete the spell, inspired by the cost. The idea is to give you a solid foundation for your glyph that you can easily add to if you're feeling inspired or leave as is. It will look nice either way sitting alongside your various journal entries.
Grimoire can be a punishing game, so make sure to consider the cards that have already come out before you decide to quest or research. Also, I suggest playing with these rule modifications if you want to reduce the difficulty:
- When you perform, simply discard the card without modifying your spells if a matching suit was drawn.
- When the prompts on a card are exhausted, don't completely remove the spell. Leave it as is.
I hope you enjoy the game! :)