Let me try to explain it:

• DEC: DEC will always be the main currency that the whole Splinterlands economy uses and is based off of. The whole in-game market uses it, and once more assets are added to the market, they will most likely be bought/sold with DEC as well.

• SPS: SPS is our governance token. I personally don't think it should be used for anything other than for staking or for governance, but the team has added temporary utility for it by allowing it to be sold for Credits, or used for certain situations like this Waka promotion. However, once SPS Validators are live and running, I'm sure we will see these situations decrease as it will be mainly used for SPS proposals, governance, and staking.

• Vouchers: Vouchers were also introduced mainly to give SPS more utility, or more specifically, to encourage players to stake their SPS. Any new asset that gets introduced into the game will most likely require Vouchers going forward. Think of it as the entry fee for "premium" assets. Anything basic most likely won't require these tokens, like the current Chaos Legion general sale.