A Sword and a key are good symbols for the logo, representing the name. Other symbols relating to themes of good versus evil, war, and combat can be used. I am not a designer, so using creative freedom is highly encouraged.
This is both a card game and a board game played on a squared but not checkered board(21x21). Cards are symbolized by numbered tokens on the board and cards have roman numerals on the back of their card to represent a game mechanic while that card is face down.
The more designs I see, the more I prefer horizontal designs rather than vertical or square logos.
Also, I like the sword and key integrated into the words, with the blade preferably in the word "Siege," and the key in "secrets."