I just got Blackchain in Technologies, and it does not seem to have actually unlocked anything. Which tab is it supposed to show up on? Is there something else I need to unlock that?
Are the Leviathans around?
When they are, having Blackchain makes it possible to exchange relics for blackcoin and vice versa. You can only buy/sell “all at once”; after the trade you will either have no more relics, or have no more blackcoin. The exchange rate wobbles around randomly but with a bias so that in the long term the value of your blackcoin holding slowly increases – until it hits 1100 relics per blackcoin, at which point it crashes to a much lower figure. So if you invest your relics in blackcoin, remember to sell up when that point approaches, and buy again after the crash.
It’s only actually worth bothering with this if you have quite a lot of relics.