The Fossil layer is one of the existing underground layers in Creativerse, where specific rocks, ores and endemic creatures can be found.
How to reach
The Fossil Layer can be found directly below the Surface Layer of any Creativerse game world.
It is easily accessible through one of the many shallow and sometimes larger Caves that lead downwards from the surface. Or you can just dig down through the top layer of the world that is most often made from soft blocks like Grass and/or Dirt and does not require any Power Cell to be equipped.
The Fossil layer is aptly named in principle for the fact that blocks of Fossils can be found here. However, since this layer already "starts" at an altitude of 80 blocks, you will be notified in the top right corner that you have entered the Fossil layer even if you are just swimming in Oceans or any other liquids at sea level. The player character is 2 blocks in height, and dipping into the water lets it reach just 1 block below the surface level, which already belongs to the Fossil layer.
Rocks and Ores
The Fossil layer is mainly made of Stone, Bedrock and Limestone. While you do not need to wear any Power Cells to mine common grey Stone, you will have to equip at least a Stone Mining Cell or better Power Cell to mine Bedrock and/or Limestone.
Nodes of Coal and Obsidian Ore can also be found on the Fossil layer in abundance, even though not many patches of these Nodes will visible in the ceilings, walls and floors of Caves; instead a little digging will be necessary to reach many more Ore Nodes.
Coal is a very important ingredient to craft a Stone Mining Cell, then Coal Torches a little later on, as well as other crafts. Coal is also a better Fuel for the Forge than any wooden blocks or Leaves. Obsidian is required to craft Obsidian Mining Cells, Obsidian Swords, Obsidian Armor, several Tools and dozens of other useful items, objects and building blocks.
Blocks of Fossils and blocks of Magnetite can be found in patches embedded in the other more common rocks of the common Fossil layer. Fossils do not require any Power Cell to be mined any longer, but Magnetite requires at least a Stone Mining Cell to be equipped. Magnetite is used to craft many different Machines and wireable objects.
Diamond Mining Cells and Lumite Mining Cells will not lose any durability when mining Magnetite, Bedrock and Limestone, all other Power Cells will. As for common grey Stone and Fossils; even Iron Mining Cell (as well as the stronger Power Cells) won't lose any durability when mining these rocks.
Common Stone can also be found in Mountains in abundance, but Bedrock - required to craft a Forge - can only be mined from the Fossil layer, so even beginners will have to visit the Fossil layer rather early in the course of their gameplay.
Under the Sand that usually covers the bottom of Oceans, usually a thick layer of Limestone is forming the upper Fossil layer instead of the typical mix of rocks (Stone, Bedrock and Limestone). Ores can hardly be found in this special Limestone layer.
Fossil layer Creatures
Several Creatures can spawn on blocks of the Fossil layer in darkness. All of them are aggressive (except if the "Pro" world option "peaceful creatures" is enabled, then they will be defensive). Most of them will come out during the night, some even during the day, where they will burn in the sunlight.
Common green Mirus only spawn on Fossil layer rocks and Stalactite layer rocks, so they are typical underground creatures, while Night Pigsies and Night Rocksters can also spawn on the surface at night, not solely on the Fossil layer.
If you are reluctant to kill peaceful animals like the yellow surface Pigsy, then you might prefer to fight Night Pigsies to collect Leather for your first Leather armor and other crafts like useful Explosives for example.
Night Rocksters are a good source of Rockster Rocks and also occasionally Magnetite. Rockster Rock which is needed to craft Leather armor, the first armor type available to players, which will help with unlocking the crafting recipes for the next tier of armor. Rockster Rock can alternatively be created from 3 Pebble's Pebbles each in a Forge though.
Miru Eyes are a necessary ingredient to craft Obsidian armor which provides much better protection from physical damage dealt by Creatures (and player characters).
Surviving in the Fossil layer
It is generally easy to survive in this layer, as long as you do not let yourself be surprised. Proceed carefully and place Moss Torches into natural Caves and mineshafts that you dig yourself to prevent more Creatures from spawning in the dark. When fighting, always try to circle creatures so that they won't be able to hit you. When Mirus cross their arms to prepare their blinding attack, simply look away.
When venturing further into this layer, you should consider wearing at least a full suit of leather armor and a Stone Sword or better, as the Creatures can be fairly tough for beginning players.
As long as you do not possess the aforementioned equipment, you can and should brew Basic Health Potions in your crafting menu from tree Flowers and Mushrooms. Put them into your quickbar, select the according quickslot and either use right-click or type the number of this quickslot to gulp down healing potions during the fight. This will help you survive your battles until you will have collected all the necessary resources from this layer that will let you create better armor and weaponry.
Taming the Creatures whose resources you need to harvest would be an alternative, but this can be rather risky to accomplish, especially for beginners lacking good equipment.