Here's a bit of what you can expect. Harvester seems like the most fun of the two modes, and bears more than a passing resemblance the Quake 2 mod, Headhunters. You or one of your teammates must then run over the skull, pick it up, and then return it to your enemy's base to score points. You can carry as many skulls as you like, and controlling the central structure becomes a question of victory or defeat. Add to all this the fact that you must then penetrate your opponent's defenses to score points with your collected skulls and it becomes a really tense game.
Overload takes assaulting the enemy base to the next level.
The point isn't so much to destroy the enemy players as it is to destroy the giant obelisk entrenched in their base. The obelisk has 1000 health points and regenerates quickly, so success means a coordinated assault where you blast it to hell all at once. Of course, you have to balance your attack of the obelisk with fending off enemy base defenders, which makes the game pretty fast paced. My favorite was the proximity mine gun, which fires small mines that stick to floors, walls, ceilings, and even players. They then go off when someone comes close to them or a certain amount of time goes by.