Fiora strengthens thanks to the Challenge Augment
Previously, Fiora’s core upgrade increased her armor/magic resistance significantly when using skills. However, this upgrade only helped Fiora tank better, making it unsuitable for the core Hero Augment position.

Therefore, in Season 8.5, Riot replaced it with the Challenge Upgrade. This Hero Augment allows Fiora to deal damage and heal based on her maximum health with every 4 attacks on enemy champions. Thus, with the Challenge Upgrade, Fiora becomes an exceptionally annoying carry with a tremendous amount of damage.
Building a composition around Challenge Fiora
Acquiring Fiora early is the first sign for players to move towards this composition. Low-cost Duelist units like Gangplank and Kayle will be good choices to maintain health. Annie is also a unit to buy when activating the 2 Bullseye threshold alongside Fiora.

In the mid-game stage, players should add Nilah and Vayne to the composition to complete the 4 Duelist threshold. Upon reaching level 6, stopping experience purchases and starting to roll for upgrades for Fiora (Vayne if possible) is crucial. This helps players reach the necessary power threshold to secure victories.

After obtaining 3-star Fiora, players should only aim for level 7 to upgrade Vayne. Twisted Fate will be a necessary addition at this stage to complete the 6 Duelist threshold. The damage reduction effect from this activation threshold helps Fiora tank and deal damage much better.

Regarding Technology Augment choices, Challenge will be the top priority for this composition. Additionally, augments like Arena of the Feathered, Trading Post, and Prize Tickets… are also very suitable for the playstyle around Challenge Fiora.
For itemization, Fiora greatly needs Giant Slayer to withstand fights. Additionally, tank items (Dragon Claw, Thornmail) or support effect items (Mercury’s Cloak, Guinsoo’s Rageblade) are all useful for this champion.
Conclusion
With the introduction of the Challenge augment, Fiora has become an extremely viable carry at this moment. This unique playstyle promises to help players climb ranks very effectively.