League-of-legends – Why does the Sapphire Crystal disappear when I purchase Catalyst the Protector

league-of-legends

I'm following this build. It says, first purchase a Sapphire Crystal, then a catalyst of protector. But then my Sapphire Crystal disappears. Why?

So I understand that a Catalyst = Sapphire + Ruby + some gold. Is that right? But what if I don't buy the Ruby, but only buy Sapphire and then Catalyst? Why does the Sapphire disappear then?

Best Answer

Sapphire Crystal is one of the ingredients for Catalyst. You can purchase the full recipe at any time, and it will automatically subtract the cost of materials you already own from the purchase price of the recipes and use those rather than new materials.