Space monsters

[Suicide Junkie]

The Pirates would help to keep the game balanced, as they are equally likely to take from large players as small players.

The first place player might lose 10% of his 100,000 minerals, while the Last place player loses 10% of his 10000 minerals.

Net effect: 1st place has 91K minerals, and Last place has 19K minerals.

The weaker players might even support the pirates somehow.