Quick answer: SteamDeckHQ scored Phantom Blade Zero 10/10 as a game but 1/5 on Steam Deck, where it averages 23-27 FPS in the Crimson Forest at the lowest settings and dips to 10 FPS. A separate test found it needs a 30 FPS lock and heavy compromises on Steam Machine.
Phantom Blade Zero, S-GAME's action RPG, is listed on Steam for an October 28 release, and SteamDeckHQ's review has bad news for Deck owners. Reviewer Noah Kupetsky gave the game itself a 10/10 but scored it 1/5 on Steam Deck, saying he can't recommend playing it there. SteamDeckHQ says S-Game provided the review copy and that the review is based on the PC version.
Even at the lowest possible settings, the game can't hold 30 FPS on the Deck. The opening Weeping Hills section runs decently, but once you reach the Crimson Forest it averages 23-27 FPS, drops as low as 10 FPS while running through the level, and gets worse in combat. SteamDeckHQ also tried MAKO and Lossless Scaling frame generation, but the input lag was too noticeable for a game built around timing, so it recommends skipping frame gen. Its test notes list 21-25W power draw, 70-75C temps and about 2 to 2.5 hours of battery.
A separate SteamDeckHQ article tested the Steam Machine. 4K couldn't hold a stable 30 FPS even with FSR Performance and dynamic resolution, and 60 FPS was out of reach: the lowest settings with FSR hit 58 FPS standing still but fell below 45 in fights. Its recommended settings are 2K resolution, medium quality, FSR Balanced and dynamic resolution set to 30, with a 30 FPS lock. MAKO's Adaptive Frame Generation felt smooth at 60 FPS on the Machine, but the input lag still caused missed dodges and parries. SteamDeckHQ called the game hard to recommend on Steam Machine as well.