you have to customise so the button's on the toolbar, then click it and enter the text you want to block - any text, of your choosing, minimum 6 characters. I'm using it for game of thrones, so no GoT or Arya, but otherwise working fine. First test: Jon Snow the news reporter (UK) entire paragraph was blacked out and i had to disable it to finish my article about politics in Turkey! It's restartless, so that's no trouble. Nice to know it works, and nice that you can add as much as you want.
I have now been using it for several weeks and it works great. Because i added 20 odd words to the block list, it can slow the browser down a bit, so i switch it off when there's no risk (shopping, banking) and switch it back on when reading newspapers, and i'm going to remove some items (eg obscure characters). This is the only blocker that isn't twitter and facebook specific which works (naming no names, but i gave the others a fair try), as an oldie who uses the internet to read bbc & guardian news, i get GoT spoilers everywhere!
Thanks a lot for your reply, it's fine as it is, it doesn't need improving i think :)