Previous Versions can be found here.Investment, added in Beta 6.6, is a Spell Card for the Integrity Deck.
It has the effect to draw a card and lower its cost by 2, at the cost of 2G. This means that you pay 2G in advance so that you don't have to pay as much later on.
You can deploy that card early, able to play a cheap monster right away. Be warned that the card drawn is random, so you may end up getting a card that costs 1G, such as Break, nearly wasting this card's effect.
Playing it early can also give you a monster with high cost, allowing to drop its cost a lot in combo with Integ's Passive Effect until you play it in the late-game. (A 9G Undyne for example.)
This card is more effective if your deck specializes in high-costing cards. If you use Lesser Dog before this, you can gain a 1G profit from its effect (or play equal if you get a 1G card).