Looking for more codes? D&D Beyond has a forum thread where codes are mentioned from time to time. at checkout at dndbeyond.com
How to use dndbeyond.com coupons :
1 – Copy the coupon/ promotion / discount code .
2 – Go to website dndbeyond.com and remember to paste the code copied to the coupon/discount/promotion box at check out page
3 – Wait for the discount and Enjoy your order