Arena Mode is an option available on the imba_custom map, which allows a team to win if the objective amount of kills is reached.
In Areana Mode, when all of a team's barracks are destroyed, The Fountain will stop attacking enemies from the moment the first wave of Mega Creeps spawns. Furthermroe, Ancients instantly kill nearby enemy lane creeps. The purpose of these changes are to enable to objective of reaching the total number of kills, and prevent the team with a lower number of kills from successfully winning the game by destroying the Ancient.
The dropdown menu for host settings when starting up an IMBA Random OMG game
IMBA Random OMG is a gamemode where heroes get random skills from a pool of available skills. Players are assigned a random hero that they will be using for the remaining game, where they are not able to repick, and they enter the game with randomly generated skills. Hosts may select the number of skill slots available, determining the number of regular abilities and ultimates that all heroes receive. Heroes may also receive the same abilities as each other.
Available Regular Abilities
Available Ultimate Abilities