I could talk for hours about Baron. He's not a hugely complicated character, but he's still got a lot of potential.
Since you've got him diamond, I can assume you know how to play him to a basic degree, so I'll skip over the basic stuff.
My usual Baron build in arena looks something like this:
-Warrior's Axe
-CD Boots
-Gauntlet of Thebes
-Ethereal Staff
-Pridwen
-Mantle Of Discord/Divine Ruin/Winged Blade/Spear of the Magus
-Sundering Axe
It's obviously changed somewhat with S8, so I'm still trying to work out if it's the most optimal, but it's still a great build regardless of what's changed.
Second thing to highlight is using his ult in the best way possible. First, you rarely want to ult someone who can get out of your ult. Track beads, track movement abilities and track CC immune abilities. Zeus with beads down? Ult him! KA just walked back from base? Waste of an ult.
Then t...