I have a helpful table I call "Monster-o-Matic". By simply rolling up random numbers, I can, on very short notice, create a very odd monster which will be a combination of random elements: Fur, scales, feather, claws, teeth, spikes, a tail, etc. I can then describe the monster part by part, and the players will be utterly mystified by what it is. If I happen to like the results, then I use the monster again. As a side benefit, the players, being the first people to encounter the thing and survive, get to name it.
Thus, players feel involved in the world, and you don't actually have to do any work, because the players will do it for you. Meanwhile, they feel special and important that they got to name a totally new monster. Don't tell them that you generated it with a table.
Should the entire party be killed by the monster(but you like it anyway: perhaps this is the CAUSE of you liking the monster), name the monster after the first partymember to fall to it, posthumously. This will inspire a suitable sense of terror and dread should the next group encounter it.