According to the card's flavor text, that fierce, slobbering thing is called a skrill, and its rider—a member of the reckless, beast-taming Grotag tribe—barely has control of it. But he's hanging on long enough to earn him the unusual creature type combination of Goblin Knight.
Now, by contrast, look at Grotag Thrasher, also illustrated by Jesper Ejsing:
When you first hear the name, you might think that this is a thrasher—some kind of giant lizard—that belongs to the Grotag tribe. According to the flavor text, the Grotag thought so too. But as you can see, the lizard has other ideas, swinging its rider around like a flail and earning it the independent, all-natural creature type Lizard. No wonder nobody wants to block it!