A long time ago, I made an Elliuki
page. I have since culled a lot from it and updated it to 5e... but expect some of the lore to be different. Essentially, there is the addition of a new 'player race' that is the greenskins. They foresaw the Games occurring and decided to establish themselves as 'people' and not just bags of loot/XP. As a result, they are one of the biggest nations around- a confederation of races including goblins, orcs, half-orcs, hobgoblins, giants, trolls, wargs, ect. They are also the most spiritual people in the world, their society revolving around priestesses and the paladins who protect them.
Clerics and Paladins exist in other cultures, but there has been a steady decline in the active worship of Gods since Gaming has become a thing...
The Pantheon is not anything established, but you can assume a God exists for most every domain. Feel free to home-brew what you'd like.
Also, I should note... teleportation and plane-shifting magic is extremely and unusually difficult to learn. Most of them are impossible to learn or cast except for the following; Arcane Gate, Blink, Contact Other Plane, Demiplane, Planar Ally and Planar Binding (Fiends only), Transport via plants, Word of Recall.
Teleport still functions, but you are considered three steps less 'familiar' with the location you are teleporting to. IE; Going to a permanent teleportation circle is 'on target' on a roll of 54-100, while teleporting to an area you have seen casually will, at best, end up in a similar area on a roll of 51-100. You cannot teleport to an area you have seen once or been given a description of.
This is why there is a business for new adventurers, as travelling long distances is in fact quite a journey by itself.
Also, the primary method of watching the games is via a Scrying spell. It's been attuned to various items that are able to hone in on your 'signal' and broadcast them on huge three dimensional projectors that are in the center of large amphitheater-like structures. Many variations of the spell exist, allowing for a variety of angles and shots and methods of viewing.
For now, feel free to consider the starting level as 1. I might go higher... but I will probably do away with XP entirely and just award a level after every encounter.