The Obsidian Heir

In the continent of Esternia, Lord Gregor Gandar the Grand is killed. A few years later a war breaks out between the house of Gandar and house of Rein while a bastard boy runs free from the grasp of a unknown house, and over in the Continent of Valeen, mythical creatures start to rise.
The Midnight Riders ride from east to west and north to south. Gandar gathers houses for war, and Rein travels the seas for war.
House Tether plans to take all of Esternia, and make it theirs. And only theirs.
Mark Gandar needs to make an heir before he is killed in war, so will he be able to make the next heir for Obsidian City?