Trial of the Four Kings is actually a solo dungeon with multiple different parts, though only the one for level 20 characters and the one one for level 40s will be open during the test phase. Darkfall, on the other hand, includes a solo mode for level 20, a 5-man easy mode for level 20, and a 5-man hard mode for level 30s. Says the studio,
“Darkfall used to be a vivid forest, home to the Palace of the King of Beasts. However, Thousands of years ago, things changed at one night. People heard loud thunders at that night, and soon the trees in Darkfall died, and the palace disappeared. Later, bounty hunters found treasures on the ruined land of Darkfall, and they believed the Palace has not disappeared, but buried underground. A huge search for the Palace started, but all of them failed. Some of the explorers never came back. People forgot the Darkfall gradually, left the ruined land undiscovered. Now only some brave adventurers are still hunting for the secrets and treasures hidden in the Darkfall.”
The closed beta begins October 25th and is supposed to be a “technical test” to stress the server infrastructure and client distribution, but it’ll clearly have plenty of playable content too.