While there are plenty of other extra turn spells, Capture of Jingzhou is one of the most efficient versions of this effect without any additional conditions
But according to a recent article by Mark Rosewater, who ran the tournament and devised the prize, "He turned in a joke card that didn't do anything." According to Rosewater's article: "I asked him for an actual submission, but never got one, so we didn't make a card for him." This retelling doesn't seem strictly fair on Rde, whose card, while silly, technically functioned within Magic's rules
For Cybertron
As alternatives, you can include Fezandipiti ex (Shrouded Fable #38), two copies of Dudunsparce (Prismatic Evolutions #80), and two copies of Surfer (Surging Sparks #187) in your deck
there are certainly times when Mana Tithe is a do-nothing dud in your hand, but its a huge swing if you ever catch an opponent tapping out for a big spell