The Shadow Crystal is originally a cursed magical artifiact created from Zant intended to destroy Midna however Link defends her and the object lodges itself into the hero's head forcing him into Wolf form permanently as a result of the twilight magic its infused with. When Wolf Link eventually comes acrossed the Master Sword the blade of evils bane releases the dark artifact out of the hero's body were Midna initially intends to destroy it however considering its power is so strong that simply touching it will cast its dark magic on the user it actually can benefit the hero by granting him the ability to transform at any point an ability that becomes crucial for the remainder of the quest. When Link acquires this item and has met Midna for the first time she can transform the hero into Wolf form at anytime and can even help him warp to the many portals left behind by the Shadow Beasts an ability that becomes incredibly useful for fast travelling.
In the randomizer its possible to gain the ability to quickly transform as seen in the HD version by pressing + so long as the button isnt dulled and Link is in a state were he normally could transform. Additionally a brand new ability comes with this item in the randomizer that being the ability to instantly change the time of day from morning to late noon or vice versa to ease searching for Poes as they are primarily seen at night time as well as to ease waiting for stores to open. To use this ability call Midna with select Talk to Midna wait until her dialogue is done scrolling then press + to change the time of day and will also reload the map. In both cases of these abilities these must be first activated in the randomizer console window which can be toggled at anytime by pressing + to bring up the window then scrolling to Midna ToD and Fast Transform.