Wizards of the Coast's adult speculative fiction line is currently at the beginning of its annual open submission season. The season runs from September 1 to February 1 of each year, and is the time during which Wizards accepts unsolicited submissions for novels from anyone, agent or no (if you have an agent, you can submit year 'round). Their requirements are:
A SASE
A one-page cover letter
A signed legal agreement
The first three chapters or thirty pages of your novel, whichever is shorter
They helpfully remind you to also please actually have written a novel, because if after the 4-6 month consideration time they decide they are interested in your work, you have to send it within ten business days. If I had an appropriate novel, I'd think of sending it their way.
The submissions guidelines, in full
They also accept submission for young adult novels throughout the year: