SlimeWar was the most recent multiplayer game. It was removed with the rest. However it was remade on FunOrb first as Ataxtix and secondly as Virogrid. It was also promised that it would be re-made in Burthorpe Games Room.
When it was on the Jagex site (which was in and around 2004) its description read:
Try to take over the board with your slime first!