Could anyone please help me with this?

Hey guys, it's my first post on reddit and I hope you could help me remember the name of a game that I used to play when I was a kid. It was an FPS game that looked like an early 2000s game ( or probably 2005-6 ), it had alines or monsters ( I can't really remember exactly which one it had ) and the most distinct memory I actually have of it that it had a grenade that was shaped like a ball in which you rotate it and split in half to use it + it had those rooms you explore. + I think the environment had weird texts like magic or something.

I know it's a lengthy post and I'm sorry for that, any suggestions of what it could be are much appreciated.