The Anniversary Edition mod package format consists of subfolders of .oni files and a Mod_Info.cfg file that provides information about the mod. (Full format description is here.) The packages then appear in the AE Installer, allowing the user to easily add the mod to his Oni installation.
Zen Garden Mod by Leus allows you to set your own battles and fully customize them, select which characters to spawn and fight, what team you're on, what items you get, and even select which sound track to play ! All in a brand new level: Junkyard by EdT
Will allow you to easily spawn and fight any character including custom characters like Iron-demon, Sarai, Motoko, Casey, Rayman ... (provided you have these characters installed)
This package is meant to be installed automatically by the Anniversary Edition: http://mods.oni2.net/node/276. If you are reading this description directly while browsing the Depot and want to install the Daodan DLL without installing the AE, place the files from the ZIP's win_only\ directory into your Oni\ game directory alongside Oni.exe. Then, replace your Oni.exe with the one found here: http://mods.oni2.net/node/231.
The Oni game application, built for Intel Macs. Requires Mac OS X 10.7 or above. If you are in 10.6 Snow Leopard, you should install the Oni Game App for 10.6 that is found under the Tools menu in the AE Installer or download it directly from here: http://mods.oni2.net/node/319.
The Oni game application for Windows; note that this will not run on modern Windows machines without the Daodan DLL (http://mods.oni2.net/node/233). This version of the app does not require the Oni CD-ROM in the drive in order to run.
New Level without Pathfinding grids, yet...
Feel completely free to make mods based on it. I don't know if it is big enough for an arena, but it is kinda cool.
For more info, screenshots, and support visit this thread.