Sinkhole shot a white ball with a trail going from white to red. When it hit the ground, it trigger 3 series of white and red line-up explosion below the surface, creating a big hole with almost vertical walls.
Damage : 4 per explosion
Upgrades
Area Strike
When this weapon hit the ground, it trigger a serie of 10 explosions in a good zone around the impact point.
Damage : 12 per explosion
Area Attack
This one does the same thing as Area Strike, but with more damage and a larger zone concerned.
Damage : 15 per explosion.
Upsides and Downsides
Sinkhole is a really good weapon, even for trained player. The main advantage is to put someone in hole with little chance of going out. Area Strike and Area Attack are more useful on enemies group.