1.12 isn't supported, didn't see that, update to at least 1.14
https://github.com/Dwight-Studio/Deepworld/blob/1.12.2/src/main/java/fr/dwightstudio/deepworld/common/DeepworldItems.java#L23
Problematic Code #14
Create your items properly.
Other things:
https://github.com/Dwight-Studio/Deepworld/blob/1.12.2/src/main/java/fr/dwightstudio/deepworld/common/DeepworldItems.java#L39
You don't need the DeepWorld. here, the prepare method is already available in the current scope.
https://github.com/Dwight-Studio/Deepworld/blob/1.12.2/src/main/java/fr/dwightstudio/deepworld/common/Deepworld.java#L46-L62
Do not log random garbage. No one fucking cares.
https://github.com/Dwight-Studio/Deepworld/blob/1.12.2/src/main/java/fr/dwightstudio/deepworld/common/block/BlockFrame.java#L30
If a type of property already exists in vanilla, it is preferential to use the existing property rather than creating a new one. In this case BlockHorizontal.FACING, as it makes intermod compatibility cleaner (eg. an item that can rotate FACING blocks can't rotate your block).
https://github.com/Dwight-Studio/Deepworld/blob/1.12.2/src/main/java/fr/dwightstudio/deepworld/common/block/BlockFrame.java#L141-L144
Don't override unless you intend to actually alter functionality.
https://github.com/Dwight-Studio/Deepworld/blob/1.12.2/src/main/java/fr/dwightstudio/deepworld/common/item/ItemDeepworld.java
Do not create "base" items that your mod items extend.
Code Style #4