By drinking this shining gold and shifting shadowy Essence you gain the following abilities.
*You gain the ability to summon the Spirits of Duel Monsters. The stronger the monster the more magic it takes to summon them. 1 to 4 star Spirits are the easiest to summon and take little effort. 5 and 6 star Spirits cost more. 7-8 star Spirits cost much more and 9+ star spirits are so costly it might be impossible for you at first. But as you grow in strength it will be easier for you to summon more powerful Spirits.
*You gain the ability to channel the power of the Spirits instead of summoning them gaining their power, skills, etc. This is less costly them Summoning them but you can only channel one Spirit at a time. You may also take on the Spirits form if you wish.
*You also gain the ability to summon a Duel Armor to channel powerful armors that channel Spirits power. This is the least costly but you may only use one duel armor at a time and the power comes from the Duel Armor and not yourself.
*The Spirits are loyal to you despite their possible personality and generally favor you unless you prove a cruel summoner. Yes, lewding them is indeed possible.
*You can apply a degree of customization to the Spirits such as changing their gender and making the more monstrous Spirits more human thus making them Monster Girls or Boys.
*You gain the ability to use Spell and Trap cards as actual spells and traps. Spells can be cast as quickly as you like but Taps need to be "set" and primed like Tula traps unless otherwise noted.
*At first you may only summon a total of 5 Spirits at a time and cast a total of 5 Spell/Trap cards but as your power and experience grows you can summon more and more at a time.
*You gain the ability to travel to any of the various Spirit Realms/Dimensions at will and you can take others along with you.
*You have a mental list of all Duel Monster cards to use however mental sorting and choosing is up to you.
*You gain the ability to Summon and use without consequences all Millennium Items.
*You have the ability and become a master of using Shadow Magic.
*You gain the power of the Gentle Darkness and become a master of it.
*You are able to physically create the various dueling/trading cards for personal use.
*You gain your own custom Duel Disk for dueling use. You can also summon other standard Duel Disks for your opponents.
*You can summon your own custom Duel Arena if you wish.
*You gain the knowledge and ability to recreate any technology from the Yu-Gi-Oh Anime and Manga series.
Note: Due to how the various card effects can react and be used I'll just say, Please Fanwank responsibly.