This currency is actually part of a larger product by Darcrus. The developers behind this project have issued three different assets, and MER is used to allow collaboration between different block chains. These communications can be time stamped, and the first use case for this is for their Jupiter platform.
This allows for document-able proof that transactions have occurred by sending that information to the public Waves chain, which this token was issued on. This also allows the main chain to remain private to protect its users, while still providing transparency to maintain the chain's integrity.
While the initial use case for this token is for Jupiter, it will be able to be utilized for other projects in the future as well. Waves allows for transactions to be paid for in the underlying token. So, the value of your Mercury investment will come from the desire for individuals to develop applications on Jupiter, which is a decentralized application platform.
The supply for this asset is fairly limited, and while Ethereum is currently the platform of choice for developers, Waves is no slouch in this regard either, and there is room for multiple solutions to exist in a market. After all, no solution is one size fits all.
Investors can buy Mercury on a decent number of different exchanges, and the trading volume for this asset is excellent. That means that you should have no trouble easily completing a trade here. There's also a variety of viable trading pairs for you to use here including Bitcoin, Waves and even the South Korean Won.
If you need a safe place to store your tokens, then you'll need to utilize a suitable wallet in order to do so. The best option here is to go to the page's official website to get their recommendation. There are several suitable options though including a couple of web wallets, some mobile wallets for Android and iOS, and the official Waves wallet will work as well. In any case, make sure that you create a backup of your wallet in a safe place. This will be the only way to regain access to your funds should your host device become inoperable for any reason.