so uh, what can yugi do agaisn't ash?
Probably start a Shadow Game/Game of Darkness (Whichever you care to call it.) to be able to use his cards in reality.
I forget if it applies to reality, but the stuff from the Milennium World arc may also be relevant, because of Ka & Ba (Some kind of life force stuff & it's sort of a simulation of the past.) where they're pretty much summoners, IIRC.
Also, the Egyptian Gods especially & as established, powerful duel spirits can manifest in reality without the need for games. Though, IIRC, they usually only do so in games, even if they may affect outside of them, like with Slifer's cloud-splitting feat. For example, the artist who painted the God Cards art was killed by them (Thankfully, Pegasus already had good painting skills of his own, so he completed their art himself.), among others involved in their manufacturing by Industrial Illusions, & when Odion tried to play a counterfeit copy of Ra (Under Marik's orders.) the actual Ra (Which he did not have a real card of.) called down lightning to strike down both Odion & his opponent in the duel, Joey.
There's also The Seal of Orichalcos, but that's OoC, even for the pharoah, the "Yugi" who played it one time & then regretted it for a long time after. (& also, he's never owned a copy of The Seal of Orichalcos; He had it temporarily when it was forcefully added to his hand via Raphael using the card "Exchange" after some set-up.)
Oh, IIRC, there was also The Eye of Timeaus, since that was able to do stuff in reality, but mostly only showed up against Orichalcos things, but it left at the end of the arc.