You are skilled at the near suicidal method of hunting involving mounting creatures mid combat to attack and subdue them. You gain the following benefits:

• You have advantage on saving throws against being frightened.
• You have advantage on Strength (Athletics) and Dexterity (Acrobatics) skill checks versus creatures larger than you.
• When you hit a creature size Huge or larger with a melee weapon attack or a thrown weapon you are attached to (like a net or harpoon) you may to climb onto it as a bonus action by moving next to it, following the rules of climbing onto a bigger creature in Chapter 9 of the Dungeon Master's Guide, and copied below.

Make a Strength (Athletics) or Dexterity (Acrobatics) check contested by the creature's Dexterity (Acrobatics). If you win, you move into the creature's space and cling to its body. While in the creature's space, you move with it and have advantage on attack rolls against it.

You can move around within the creature's space, treating it as difficult terrain. The creature's ability to attack you depends on your location on it. (I suggest it just has disadvantage and leave it at that). The creature can dislodge you as an action by making a Strength (Athletics) contested by your choice of Strength (Athletics) or Dexterity (Acrobatics).

Harpoon: martial melee weapon, 1d8 damage, versatile (1d10), thrown (20/60), you may grapple a Large or smaller creature you hit with the harpoon until they remove the harpoon by breaking the grapple or the rope is cut (AC 10, 5 hit points). While they are grappled in this way they may move within a 20 foot radius around you.