As the main antagonist of Bowser’s Fury, you will be seeing Fury Bowser quite often. When you begin the game, you will see the dangers of Fury Bowser in the opening sequence. When he appears, the weather will turn from sunny to rainy, although you can see a little bit of rain right before he appears. Once he fully appears, the sky will also turn dark and Fury Bowser’s effects will come into play. Not only will he spit fireballs into the sky, which will come down as little meteors, but those meteors will leave hotspots on the ground.
In addition to the falling meteors, blocks will also fall to the ground, which will embed themselves as permanent fixtures. Some of these can be used as platforms, although some will be a little too high for Mario to reach. The last thing you will see from Fury Bowser, while you’re normal Mario size, is a breath attack. You can usually tell this is coming, as the ground will turn a reddish orange color, so you will need to find cover. Any piece of solid land will work as cover, but the blocks that fall from the sky will also work to block the breath attack.
However, you can also use the breath attack as a means of destroying the Fury Blocks, which are the grey-colored blocks with Bowser’s face on them. In fact, that is the only way you can destroy them, since they are usually hiding Cat Shines behind them. Fury Bowser typically appears to do his thing every 5-6 minutes of in-game time. After around 90 seconds of so of terrorizing Mario, he will leave on his own, although collecting a Cat Shine will also send him away. Sometimes, though, the sky will turn a red color and Fury Bowser will not leave on his own, which means you must get a Cat Shine in order for him to go to sleep once more.
The last thing that should be mentioned is the cats you will find throughout the various islands. Normally, they are friendly, although they will only gather around Mario if he has the cat power-up (they run away otherwise). However, whenever Fury Bowser is out and about, then the cats will turn into Fury versions of themselves and come attack you. There’s nothing you can really do about them, so it’s best to just avoid them altogether.