Trip Strike

Try a contest of Roguery, Strength, or Weapon Skill
against the target’s Strength or Agility to trip the target.
Weapon Skill: Roll to hit instead of rolling a test of skill.
If you win, the target is tripped and knocked prone.

You cannot use other techniques with this attack.

Prone:
Your melee attacks have disadvantage.
You are off guard against melee attacks (melee attacks against you have advantage).
Ranged attacks against you have disadvantage.
Every 5 ft. you move costs an extra 5 ft. of movement.
If you can move, you may spend movement equal to half your speed to stand up.
Dashing only gives you half as much movement on the turn you stand up.

Prone and Flying:
A prone creature which is flying is immobilized, unless it has the ability to float.
An immobilized flying creature begins falling, unless it has the ability to float.
A flying creature may spend an action while falling to end the prone condition (and accompanying immobilization and falling), if it is not also immobilized for another reason.