Built with GMS 2 and tested for GM 8.0. This is a grid-based shadow casting with multiple spectators. Ideal for party-based RPGs with map exploration and turn-based combat, like Spiderweb Software games (Exile, Avernum). It uses a raycasting method and a couple others to decrease workload and allow for mutually overlapping explorations. It manages unseen cells (black) and already seen cells (semi-transparent). You need to be familiar with the ds_grid functions, but you do not need surfaces. Easy to implement in any other projects. Commented in detail. To my knowledge, a squad dungeon crawler has not yet been done in Game Maker after all these years. There are many party-based, turn-based RPGs on Steam, but none in GM yet. Will you be the first?