User blog comment:BannedLagiacrus/Monster Appreciation Week: Grimclaw Tigrex/@comment-27125903-20170210181200/@comment-33581177-20170210214644

It's a DLC quest, you had to kill serveral monsters in the arena (G-level of course) Here are the monsters in order as they appear:

1) Nargacuga 2) Tigrex 3) Black Gravios 4) Black Diablos 5) Furious Rajang

It was the second hardest quest in the game, the first one being the White Fatty DLC quest.