Yellow Sign

Yellow Sign is a relic located in Holy Forbidden. Once collected, it unlocks the passives Silver Ring, Gold Ring, Metaglio Left, and Metaglio Right, which will all be available as floor pickups in all stages (excluding Eudaimonia Machine, Tiny Bridge, and Bat Country), permanently. Additionaly, Treasure Chests containing evolution will become silver. It is also required to unlock certain secret characters and events. 
==Obtaining==
Yellow Sign is located following the path east in Holy Forbidden, the stage itself being unlocked by defeating the last boss that appears in Moongolow with a non-secret character. Its location is also tracked by a green arrow on the player's screen. Once Yellow Sign has been collected, Holy Forbidden will no longer be accessible. 
Alternatively, the Yellow Sign can be unlocked in the Forbidden Scrolls of Morbane by casting the Spell "ihaveseenitihaveseenitihaveseenitihaveseenitihaveseenitihaveseenitihaveseenit". 
==Trivia==
*There is a 1 in 65535 chance for yellow squiggles to appear over the icon in collection. The squiggles are random every time. However, the icon will disappear after 9 seconds and the player have to scroll down the menu to see it. Making it very easy to miss when people take too long and/or have no incentive to scroll down.
*Yellow Sign is a reference to 'The King in Yellow'. It is written by Robert W. Chambers, and is known to be inspiration to H.P. Lovecraft's writings. In the book, it never fully describes the shape and purpose of the Yellow Sign, it is described as "a curious symbol or letter in gold. It was neither Arabic or Chinese, nor as I found afterwards did it belong to any human script".
**In 'The Repairer of Reputations', another of the stories in the collection, suggests that anyone who possesses or sees – even by accident – a copy of the Sign is susceptible to some form of insidious mind control or possession by the King in Yellow or one of his heirs. The stories also suggest that the original creator of the Sign was not human and possibly came from a strange alternate dimension. This may explain why there is a shadow of a pair of hands cast on the screen, congratulating the player after getting the Sign or defeating the Ender.