Sisay, Weatherlight Captain

The five-color activation is a fixed cost no matter what it retrieves, and that flat pricing is the design's whole gambit: one of each color puts a legendary permanent straight onto the battlefield, turning a plain 2/2 into the front of a toolbox chain. Each activation raises the ceiling for the next, since the search wants a legendary permanent with mana value less than Sisay's power, and every legend you resolve that adds a new color feeds the +1/+1 pump. So the sequence compounds: land a multicolor legend, Sisay swells, the threshold climbs, the next fetch can be bigger. Critically, the pump reads off color diversity, not raw legend count, which is a subtler build constraint than it first looks: five mono-white legends only ever contribute the color white, for a total of +1/+1, while a spread of gold ones turns the tutor into a snowballing engine. This is a rework of an earlier Sisay who searched only for legends to hand and never threatened to run away with a game. The newer version keeps the card advantage (a card resolving from library to battlefield is still a card gained) but stacks mana advantage and repeatability on top, pinning its own size to a stat other permanents you control determine. The mono-white face is a disguise; underneath is a WUBRG value engine that demands a board both legendary and colorful before it does anything at all.