Arena

The Arena is a combination of two new game modes featured in the 1.5 update: Sandbox and Competitive. These game modes are available from the main menu, and allow for local multiplayer of up to four slugcat fighting, eating, and exploring in a variety of Arena maps. The four playable characters in Arena mode are the Survivor, the Monk, the Hunter, and the Watcher. Many creatures, items, and maps of these modes are initially unavailable and must be unlocked by finding collectibles in Single Player.

Sandbox
This game mode allows the players freedom in crafting their own arena experience, with readily accessible map editing feature and customizable objectives. The menu screen of Sandbox allows for detailed control of the arena rules.

At the sliding menu to the left, the players choose among unlocked arena maps to play on. Immediately next to maps are several sliders to change the number of points rewarded for completing objectives, including slaying of unlocked creatures.

Below character selection are check-boxes to allow players to spear each other, make enemies more aggressive, and activate the map's developer chosen spawns. Beneath this is the option of end-conditions for a given round: playing until a desired score, a playing until the rains come, or no restriction. Duration of cycles can range from 0.5-10 minutes or can last forever.

In the Sandbox, the players are allowed to switch freely between a map editing mode and live play. The locations of creatures, food items, weapons, and even player spawns can be controlled in the map editor. A slugcat can only spawn at a tunnel, and will spawn randomly if one is not selected. In the bottom right of the map editing interface is the option to randomize creature spawns, switch between preset map configurations, and to initiate live play. Switching between live play and the map editor is also possible via the pause menu.

Competitive
This game mode encourages quick hop-in hop-out sessions where players compete towards objectives including food consumed, time survived, and creatures slain. Competitive mode is setup for the creation of round playlists, wherein several maps can be played sequentially without interruption. A second slider near the map selector allows for customization of that playlist, with the option of randomizing all maps chosen.

A checkbox to the right determines the number of times from 1-5 each map in the playlist will be visited. Above that slider are check-boxes to control the ability for players to spear each other and the aggressiveness of AI. Even the length and pacing of a round can be controlled, with duration of cycles able to be set from 0.5-10 minutes and the quantity of creatures ranging from non-existent to overwhelming in quantity.

Unlockables
Unlockables earned in Single Player are shared between both Sandbox and Competitive difficulties. There are 34 playable maps, with Amphitheater, Frame, Levels, Platforms, and Warehouse initially unlocked. In Arena mode there are also 59 objects and creatures, of which slugcats, green lizards, magenta lizards, batflies, rocks and spears start unlocked.

Trivia

 * The first three player models are from Single Player's different difficulties. The Watcher is unique to Arena mode.
 * All slugcats in Arena mode have the physical aptitude and abilities of medium mode's Survivor from Single Player.
 * Players enter Arena mode via tunnels normally representing room transitions. These tunnels change into shelters as soon as the end-condition is met. For Competitive, this is as the rain is approaching or when there is only one slugcat remaining.
 * Creatures, items, and maps available in Arena depend on the unlocks found on the currently loaded save profile. The ecosystem of a particular map may vary greatly depending on the save loaded.