Which is worse? Something that can have survivors or something that would wipe out an entire planet regardless of intelligence, Strength, speed, Or any other positive attribute that would possibly save the entity in question.

Bam. Sponges.

They absorb things right? What makes these sponges “Killers”? If it absorbs water, (Which, They don’t, unless their dead. they filter water through themselves.)

It would be a problem but only if they somehow stopped the process of evaporation. Kinda hard to do that considering.

Alright, So they don’t absorb water. What do they do then?

They absorb air. Let’s assume that these particular sponges need oxygen for food and procreation. That would mean that the more sponges bred, The more oxygen was used, and the more sponges would be there to bred and so on.

eventually, the planet (E.I. oxygen producing algae.) Would be overwhelmed and the sponges would continue to put more pressure on it until there wasn’t enough air for animal life. Even then humans could conceivably manage it. But if were talking about using anything other than Bio-Dome like cities,
(Self supporting using rescued plant life in theory. But various trials have proved that our current level of technology is insufficient to sustain a closed man-made environment.)

The population would then decline and eventually go extinct. Then your only left with plant life which has no way to combat the threat. (We’re Totally FUBARED at this point by the way. Gone. Everyone’s Dead. Unless they escaped the planet or used the method I mentioned previously.) And eventually, barring an unforeseen external intervention, the sponges (still breeding exponentially at this point,) would overtake over take the plants, Starve them of oxygen, and drive them to extinction. At which point, With their food source denied, The sponges would start to die off and eventually go extinct. Leaving only the husks of our world’s once great civilizations.

And this is why I shouldn’t be allowed to stay up past nine ‘O clock.

Mono the elderish.