Invasion is a 6v6 objective mode, first introduced in Halo Reach (2010) where two teams (Spartans vs Elites) face off against each other. Each team takes turns attacking and defending. The goal either being defending different objectives, or capturing three phases of objectives to win the round.
Each team is divided up into 3 fireteams of 2, one fireteam for each the left, right and center lanes. When setting this up in forge, initial spawns need to have spawn sequences set to either 0, 1 or 2 for fireteams 1, 2 & 3 respectively, with the team colours for the object set to red or blue depending on which faction you are setting the spawns for.
For respawn points, these will only be necessary at the start of the game or very niche points during mid-late game incase of a bad spawn or a player joining late into the game. In terms of forge, these are set up almost identical to initial spawns; however you will want to use the “invasion” game type label to make sure they are only used at start.
For respawn zones, you can use either the respawn zone object or the hill marker object. Using the hill marker object is much better and easier for invasion as the point on the object is where the camera will be facing in the respawn screen during gameplay, so this makes it easier to position where you want players to be able to see.
When forging invasion there are some very unique and key game type labels which can be set on objects in forge via the objects settings menu, these are fundamental to the gameplay to make it work, but can also be used creatively to make a unique experience that no other mode in halo can offer.
These labels are as follows:
This label checks for the current phase via the spawn sequence then deletes the object set with that label at the end of the phase. For example, a wall double has a spawn sequence of 1, with a label of invasion gate, this means the wall will be deleted at the end of phase 1. This allows forgers to create opening pathways or debris after an objective has been completed.
This label sets which phase the respawn point, hill marker or respawn zone will be used in, whilst the spawn sequence just like initial spawns, sets which fireteam the spawn will be used for.