I was inspired by Water Sports and Mud Sports, but wanted to create techniques that would actually be useful.
Here's a technique that protects each type against its weakness:
Sinkhole (Water): Earth moves do half damage for X rounds.Drought (Fire): Water moves do half damage for X rounds.Steel Beams (Metal): Fire moves do half damage for X rounds.Verdigris (Wood): Metal moves do half damage for X rounds.Salt (Earth): Wood moves do half damage for X rounds.
These look good! I also like techniques that affect the battlefield. I'll look into trying to implement these as a technique effect in the future.