Yet *another* miracle card in a long line of Avacyn Restored miracle cards:
Well, the latest white miracle card is spoiled and it's the bigger, badder counter part to Banishing Stroke (white's other miracle removal spell). It's odd that both of their miracle costs are just a single white... but I supposed the raw power of wrath type effects is completely dependent on timing. If your opponent has more creatures on the battlefield, wrath effects are good for you and vise versa. I guess it makes sense that an effect that removes your ability to time the effect is solely responsible for the discounted cost.
Without library manipulation, I think this is a terrible card, at least in constructed. In limited, a wrath at 6cc is still a wrath and in a block that features things like undying, it's important to note that the creatures aren't "destroyed." Undying won't trigger on creatures whenever Terminus is played.
If I were to make a deck based on Terminus, I'd want to abuse the fact that creatures are placed on the bottoms of their owner's libraries. This means tutor effects and this means this deck is for casual use only. I'm talking things like Squadron Hawk or maybe even Spirit of the Night (of all things). This means these deck would have to be slow-ish control decks that can pay for the hard cast of Terminus, but also benefit the most from the constant reshuffling of key creatures.
Okay, so this deck idea was a bit of a stretch, but like I said, I think Terminus is a bad card.