If you want beat Lava Stone Boss,you'd better reach lvl 80+.your using all lvl 80+,so that you wont need a buffer, but Slade has a pretty powerful move he does maybe once every 2-3 minutes that 1 hit kills 90+ valks. so a buffer couldnt hurt. A savage with max shout wouldnt hurt either.The following are some tips on Lava Stone Boss.Hope it is helpful to you.

As far as the setup goes...
1. lvl required : I think better to come at 80+ with some cronous cro.
2. put your party on bridge, give one responsability of killing the way at enter till bridge, another same thing but for the way going at right, one begins from the tree, and anothers can go at the big place b4 all begin to kill, if they can take hits from there easy. All have to begin to kill at same time, easy to give one the responsability to say "go" and all others follow.
3. Put your best AoE characters in the main room.
4. think to destroy the 2 stones which appears at same time than boss, before killing the boss himself.
5. have at least a buffer, many valks

If you can`t get it down to around 10 monsters with this setup you`ll probably need two parties to succeed. Oh, and killing slade is the easy part, although he does teleport around the map to a few different locations at random.

That's all for this guide,do you learn some useful from it?Have a good experience in cronous cro