Lineage System

The Lineage System determines which creature type will re-spawn in a den when killed by the player. This only affects certain dens in game; normal dens only ever spawn a single type of creature.

Explanation
When a creature is killed by the player, there is a 33% (50% for Hunter) chance per cycle of a new creature spawning in the parent den. For lineage dens, when that creature respawn chance is fulfilled, there is an additional chance that a different type of creature, usually another colour of lizard, will instead spawn based on a predefined lineage list. This is the only way to encounter red lizards in game as Survivor and Monk.

Information on Lineage lists for specific dens can be found in Rainworld > World > Regions > [specific region] > World.txt, as well as in this interactive map Made by Henpemaz

Examples
In this image, SU_A40 shows the room code, and : 2 : is the den number. The first type of lizard to spawn in this den will always be green. When killed by the player, there is a 10% chance (0.1 out of 1.0 total) that the next lizard spawning will be pink instead. Every time pink is killed, there is then a 50% chance of changing to blue, and so on. The red lizard here will re-spawn infinitely, since there is a 0% chance of progression. In this image, the NONE value means that nothing will spawn in that den from game start, with a 5% chance per cycle of a pole mimic appearing. After it is replaced with another mimic (40% chance per kill), there is then another 40% chance that a tentacle plant will instead appear.

Curly brackets { } indicate the size of the creature, if applicable, and can also be seen with centipedes.