Longleaf Valley: Special Serum Explained

Special Serum is a very special item that can be used to merge with any other item, except for a producer, to create the next item in it's merge chain.

Special Serum is very hard to get, and probably one of the rarest items in the game, so should be used absolutely only when needed.

To get serum into a usable state, you need to merge it to level 4. Then, find the the item that you want to merge it with and drag it on top of it on the game board.

So for example, in the Tools merge chain, if you have a level 11 watering can you can get the level 12 wheel barrow by dragging a level 4 special serum onto the watering can.