I'm in the process of making a game. The world happens to have multiple regions and types of land, but I'm at a loss at how to transition from, say, grasslands to mountains without making it seem abrupt. If anyone has thoughts or suggestions, they'd be greatly appreciated. Thank you.

Well a lotta people use world maps, that way the areas themes are sorta self-contained.
However, you could just subtly remove common elements of what defines each area as you progress from map to map and slowly add in elements of what would become the next. Ie, travelling from a grassland to a desert you'd see less shrubbery, maybe add in some patches of dead grass, a few tiles of sand...I'm sure you'll see where I'm going with this.


And welcome to the forums

Unfortunately, world maps are out of the question as I plan for an almost completely open world. I will try to blend the elements a bit, however, thanks.

for vx , parallax

That would improve the quality of the graphics, but its the content that he's asking for.
Besides anyone competent enough at mapping to parallax probably wouldn't even need to ask this question.

Hopefully this is a good example.
As you see, the grasslands (which could have less trees if you want) transitions by slightly forming on the mountain.