Set loose in a basement

You have no idea where you are, but it's dark.

A voice comes over some intercom system. "Welcome, human. You have been selected to become a mother of our race. You see, we are actually hybrids, born from humanoid creatures that once inhabited this planet. The Vroggn, from another dimension, captured and subjugated this species, making them slaves to lust. Unfortunately, the last of that race has died, and we are unsuitable for creating more of our own. Therefore, we have captured members of your race suitable for continuing our own. Prepare yourself to meet the Vroggn."

A door slides up at the other end, letting in some light. A massive blob slides into the room, several tentacles swarming up from its body. The sight frightens you, but also makes you incredibly horny.