- "King Mern allied us with the Rock to repel the upstart's army. One can only marvel that King Mern did not reconsider when he saw the living dragons against him. Perhaps he should've sought counsel from his trusted stewards before he set out. Then again... perhaps he did."
- ―Margaery Tyrell
King Mern IX Gardener was the last of the Gardener Kings of the Reach. When Aegon the Conqueror invaded Westeros, King Mern joined forces with Loren I Lannister, the King of the Rock, to face Aegon in battle. Their armies met at the Field of Fire, during which Mern himself was killed, and his kingdom fell to Aegon.
At first the united armies of Loren I Lannister and Mern IX Gardener seemed to be winning, pushing back Aegon's troops. However, once Aegon unleashed his three dragons - Vhagar, Meraxes and Balerion the Black Dread - even the combined might of the Kingdoms of the Reach and the Rock could not stand up to them. Four thousand men perished, consumed by the dragons' fire, earning the site of the battle the name of 'the Field of Fire.' Among the dead were King Mern IX himself and all of his sons; thus the Gardener dynasty became extinct. Mern IX's steward, Harlen Tyrell, surrendered Highgarden to Aegon and was named Lord Paramount of the Reach, Lord of Highgarden and Warden of the South.
It is possible that King Mern IX wasn't inclined to a war initially, since it would have likely been a sure defeat, but it has been suggested that Lord Harlen Tyrell had suggested that to King Mern IX that going to war to not appear weak and cowardly, with the intention of claiming the Reach for himself.
In the books
In the A Song of Ice and Fire novels, Mern's story is the same.
Kings of the independent Seven Kingdoms
|Kings in the North|
|Kings of the Rock|
|Kings of the Iron Islands|
|Kings of the Reach|
| Kings of the |
Mountain and the Vale
|Princes of Dorne|
|Kings of the Rivers and Hills|