I’ve looked around somewhat and was saddened to see a lack of arena games. There are references to a game in Gulg with the Ahguda Dok, and the Dok, as well as the Pelota… but I’ve found no game references, and no specific rules. Here’s one I sat down and play tested, and it seems to work pretty well. It’s a bloodier sort of soccer, hockey, lacrosse mix. I’m open to ideas and suggestions for improvements, including a name.

Game Layout
Two goals 15 ft across equidistant from the center of the ring.

Ball is a modified pelota, tiny object AC 7 (10-5 Dex+2 size) Variants can be played where this is a improvised weapon due to a re-balancing of the ball (IE -4 atk rolls made)

Every 5 ft the ball moves, the ball’s AC increases 2.

Each team is provided a number of healing fruits equal to the number of players. The fruits are located on a shelf behind the goal at the start of the game.

Each player is fitted with a slave collar that is capable of dealing damage to any and all players on the field. Dealing the damage is a free action, and up to the referees who oversee the game. Unscrupulous referees have been known to overlook some infractions, however, in clearly biased games, referees have been known to go missing.

The pelota starts play in the middle of the field.

Weapons for the team must be agreed upon before the start of the game. If no agreement can be reached, 1 swatter along with 4 mauls are provided. As a general rule, melee weapons should be bludgeoning, and ranged are usually modified to be the same (dealing non-lethal damage)

Scoring
No goal is tied to a team. Scoring is accomplished by moving the pelota across the line at the front of a goal. The goal is always accredited to the team that initiated the movement of the ball. Tips and attacks of opportunity to reverse or otherwise move the direction the pelota are not considered during scoring. A stopped or caught pelota is a reset point for this.

Moving the ball
A successful attack moves the pelota 5 ft + 5ft per 5 damage, rounded down.
Ranged weapons, psionic attacks, and magic all count toward this movement.

In addition, the pelota can be picked up by anyone entering its square, and making a successful attack. This attack provokes attacks of opportunity from any adjacent character. Once picked up, a character can move 5ft with the pelota. Moves further than 5ft deal 1d10/5ft to every ally on the field via the slave collars.

The pelota has a thrown range of 10 ft. (max range of 50 ft as per phb pg 134). In games where dejadas are used, the win limit is often raised to make the game last and the max range is 150ft. To pass the pelota, a ranged touch attack is made, along with an attack of opportunity by the target.

If the range touch attack succeeds, and the attack of opportunity fails, damage from the attack is rolled per normal rules (1d4+str or 1d6+str). If the ranged touch attack fails, splash weapon rules apply. If the pelota lands in an occupied square, an attack of opportunity can be made, as long as the target still has attacks of opportunity to take.

If the range touch attack fails, a random direction is chosen with 1d8, and the pelota lands a number of squares away as per the range increments.

A pelota provokes attack of opportunity as per a creature moving through or by a square. Since no one is on the pelota’s team, anyone may make these attacks, and they fall into two basic categories. Catching and striking.

Catching – A pelota may be caught as an attack of opportunity if it is thrown through a square of a character. The AC of the pelota is equal to 7+the intended end location. Thus someone intending to throw the pelota 20ft, and an attempt to intercept it was made, the AC would be 7+(2×4)=15. Catching provokes an attack of opportunity on the character, but not on the pelota.

Deflecting – A pelota may be deflected by any attack of opportunity. The pelota’s AC is equal to 7+the distance it has moved. Thus a pelota having moved 5 ft would have an AC of 7+(2×1)=9. To determine the effects of the deflection, move the pelota to the designated spot, then move it the direction and amount deflected. It is important to note, this is not the actual path of the pelota, and it is merely the end location. To determine if secondary tips can be made, a line from the initial tip must be drawn to the end location. The first character in that line may make an attack of opportunity, with the catch AC being equal to the original catch AC.

Additional Rules
To keep the game from becoming a brawl, a character may attack any other character within 5 ft of the pelota. Any attacks away from the pelota result in 1d10 dmg/2 damage dealt. The standard referee has a spot check of +15 vs bluffs to hide cheap shots.

Flying more than 5 ft from the during a game is not illegal, but it is strongly frowned upon. A team made entirely of Aarakocra did this once, upsetting a local favorite. Next game crossbows were installed around the arena, and the Aarakocra did not fare as well.

Interesting game.

The Dragon Crown adventure has an arena game in Urik that is played with a spike-covered ball or sometimes a severed head.

So I’ve been remiss in writing more about this topic. I will get the Bard’s Gambit game in here, despite it being a gambling game and not an arena game. However, as Band2 pointed out, Dragon Crown has a game in it called Death Ball. So here is what I can make of it from the Dragon Crown adventure.

Death Ball

Object: Score as many goals as possible on the opposing team’s side of the field. There are a total of 5 balls available.
Rules: Teams must start on their starting lines.
Balls must start in the center of the field.
Hostilities must end when the game ends (ie 5th goal is scored)

You may attack the other teammates using any means available.

The Field

160 ft wide
290 ft long
The curve for the ends of the arena start at 80 ft from either end, which is where the starting lines are located.
Raised dias is 20×20 ft with the goal being 6ft high (I would raise it to 10 or even 15 to require some sort of jump check)
10 ft away from the wall, but centered (lengthwise) in the field are two 20×30 ft giant scorpion pits that are 10 ft deep each containing 1 huge scorpion.

Scoring a goal

This is where my 2nd edition stuff gets shaky.
(2nd edition)
You physically have to push the ball into the goal, that closes a trap. You then make a Dexterity check at a +3 to pull your arm free, or take 3d6 damage.
(3.5)
I think this translates to a reflex save DC 16 but I’m not certain. I don’t remember what 3d6 translated to, but I think it is still pretty much the same.

Passing the ball

(2nd edition)
Dex check at a 2 must be made when attempting to pass or throw a death ball. Failure causes 1d3+2 to the thrower or 1d6+2 to the catcher. It acts as an attack against the opponent as an unadjusted THAC0 roll.

(3.5)
So, again, reflex save DC 15 to throw or catch the ball, and you throw it as an attack against the AC of your target. Could also just change this to a dexterity check DC 12(?). (Again, I would implement attacks of opportunity for deflection purposes, but it depends on how complicated you want to make the game)

You cannot score a goal by throwing the ball in.

The Pits

(2nd edition)
If you are hit near the pit, and you fail a dexterity check, you fall in. A rope is available to climb out, and it takes 2 rounds to do so.

(3.5)
Hit with an attack near the pit make a dexterity check DC 5+damage taken or tumble in.
Normal climbing rules apply: DC 5 for 1/4 speed. Can take a -5 penalty to climb at half speed. Denied dex when climbing. If climbing in a corner the DC is reduced by 5.

Spiked Walls

The game actually talks about impaling people on the spiked walls, but it doesn’t discuss how to actually throw them up there. It does note that you take 3d6 damage.

Searching the web I found the Toss feat which requires a Dex of 13, Improved Unarmed Strike, and Improved Grapple. It is a grapple check, and every 5 you exceed your opponent, you throw the opponent 5 feet. In addition you can throw them 5 feet for every size catagory you are larger than them. If you succeed, but do so by 5 or less, you throw the opponent 5 ft, and they take no damage. Damage done is 1d6 per 10 feet thrown as per falling rules. In addition, the opponent’s weight cannot exceed your maximum load. (I think this would work)