Welcome to the Gateway of Chaos
Black Luster Soldier (BLS for short) is an archetype used by Yami Yugi , Yugi Muto and Yugi Muto (DSOD) that focuses on banishing Light and Dark monsters to summon the archetype's boss monsters. A BLS deck usually is a beatdown deck, using spells and small monsters to deal with the opponent's interruptions and using the boss monsters to close out the game.
Skill
There are 2 skills supporting Black Luster Soldier: Master of Rites: Super Soldier and The Soul of Light and Darkness . This guide will be focusing on decks using The Soul of Light and Darkness because they are the most popular and competitive, since the skill Master of Rites: Super Soldier requires you to have a BLS ritual monster and a monster to serve as ritual material in your hand while The Soul of Light and Darkness already sets up your graveyard with Light and Dark monsters and a Loading... , requiring only that you special summon a BLS monster to get a ritual Black Luster Soldier from your deck and get up to 3 banished cards back on the graveyard (you must have at least 1 card on the banish pile to activate the skill).
Core cards
These are the bare minimum to competently play this deck:
Black Luster Soldier
The OG Black Luster Soldier is one of the most important cards of this deck because if you manage to stick him (or Loading... ) on the field, you can get a ritual spell along with your BLS when you activate the skill.
There are 3 reasons why you want to run only 1 copy of Loading... :
1- You don't really want to summon him turn 1 because the skills sets the ritual spell in your backrow, meaning it will be vulnerable to your opponent's backrow removal cards. If your opponent manages to remove your ritual spell and you only play 1 ritual spell, you'll be depending on the Loading... in your graveyard and in your Loading... from then on.
2- You can only get the ritual spell from the skill once.
3- The Soul of Light and Darkness prevents you from getting a BLS ritual monster that is already on field or on graveyard, which means that if you already have Loading... on field or on graveyard, you cannot add another copy of him via skill. This reason also applies to the other Black Luster Soldier monsters being recommended to play mostly at 1 copy.
Black Luster Soldier - Super Soldier
If you're going first and you have to open with a BLS ritual monster, this is the one you'll want to see since he can float on destruction to any of your Gaia monsters on the graveyard. Not to say he isn't useful on other turns, you can make some really cool plays by crashing him on a opponent's 3000 atk beater and floating to a Gaia monster to deal damage or just ran over your opponent's monster and deal burn damage. He is usually is the starter if you only have him to activate the skill and a plan B if things goes wrong. Is the Loading... starter of your push plays, but it's usually the BLS you'll search for the first time you activate this skill. That leaves the role of finisher to...