Well, first off, AO3 is a great place to start. It has a very comprehensive search function. Just type in 'celtic phoenix fixing rwby' in the search bar and see if it pops up. Fanfiction.net is also a possibility. Another option could be some RWBY - specific fan forums. Sometimes fans will share their favorite fanfictions there, and someone might know exactly where to find this particular one. But AO3 and Fanfiction.net are your best bets overall.
I'm not entirely sure specifically what that fanfiction is about as I haven't read it. But generally, in RWBY fanfictions, 'fixing' might imply that the author is trying to correct or improve certain aspects of the RWBY story. The 'Celtic Phoenix' could be a character, an idea, or a symbol within the fanfic that plays a key role in this fixing process.
Improving your RWBY fanfiction while fixing it involves several aspects. Firstly, the relationships between characters need to be accurate. For instance, Blake and Yang's relationship development should be in line with the show. Secondly, the action scenes should be exciting. Use detailed descriptions of combat moves, like Ruby's scythe - wielding techniques. Thirdly, be careful with the lore. Don't create new rules for things like Grimm behavior without a good explanation. By taking care of these elements, your fanfic will be much better.
You can try fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfictions, and you can search for 'Harry Potter Celtic' in the search bar. There are likely to be many stories there that combine the two elements.
One tip is to check for consistency in the characterizations. Make sure the fanfic characters act like they do in the original RWBY series. For example, Ruby's optimism and love for weapons should be maintained. Another is to fix grammar and spelling errors. Poor grammar can make the reading experience bad. Also, ensure the plot makes sense and doesn't deviate too much from the RWBY universe's rules and themes.
Fanfiction.net is also a great place to look for RWBY fanfiction. There are thousands of stories written by fans from all over the world. Just search for 'RWBY' in the search bar, and you'll be presented with a plethora of options. Some stories are really well - written and can offer a new perspective on the RWBY universe.
You can try fanfiction websites like Archive of Our Own. There are a large number of phoenix fanfiction works there, and you can search by tags to find the ones that interest you most.
You can start by looking on fanfiction websites like Archive of Our Own or FanFiction.net. They have a large collection of various fanfictions and there's a good chance you'll find some about Marco the Phoenix there.
You can start by looking on popular fanfiction websites like FanFiction.net or Archive of Our Own. These platforms usually have a wide range of fanfictions, and you might be able to find some Takara Phoenix ones by using the search function.
There are also some Naruto - specific fanfiction forums where fans share their own works. You might be able to find Naruto Phoenix fanfiction there. Additionally, some Naruto fan groups on social media platforms might recommend or even host some great Naruto Phoenix fanfiction. Just be sure to respect the rules of each platform and the rights of the fanfiction authors.
You can often find Celtic themed graphic novels in local comic book stores. They usually have a section dedicated to different themes, and Celtic - themed ones might be there. Another option is online platforms like Amazon. They have a wide range of graphic novels, and you can simply search for 'Celtic themed graphic novels' to see what's available.