This is the first mission that you get in the beginning of the game. After you wake up in the field, you are then directed to the castle, where you will meet someone that (vaguely) explains the situation going on. You are then told to go to the guild for more information. There, you will meet Guildmaster Vilnar who tells you to do the mission for information. After heading out to Elna Plains: Land of Beginning, you will have to defeat a Blue Lizard in order to fulfil the mission requirements. Amongst the Blue Lizards are also some Gremlins.  After successfully finding and defeating a Blue Lizard, you are directed to head back to the castle and guild. Once you reach the castle, the mission is complete.

Description from mission log:

"Target: Defeat a Blue Lizard, found around Elna Plains: Land of Beginning.
Requested By Guildmaster Vilnar
Let's start with a test of your skills. Defeat one of these monsters, which you'll find on Elna Plains."

After accepting mission

Upon returning to town