There are three steps to Living End:
Step 1 - Throw as many creatures as possible in your graveyard. Living End utilizes creature cards that not only allow you to discard them into your graveyard, but that are self-replacing. Most accomplish this through cycling, paying 1 mana to pitch the card and draw another.
This creates a powerful engine where you easily draw the land, creatures and combo pieces you need. It is not unusual for this deck to go off turn 2.
Step 2 - Cascade into Living End. Cascade is a very, very broken mechanic. When you cast a cascade spell,, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.
In living end, you have multiple cards which cascade, but only one valid target in your deck: Living End. This means that when you do choose to cascade, Living End will be the card you cascade into 100% of the time.
Step 3 - Profit. Living End destroys destroys all creatures in play and simultaneously brings all creature cards from the graveyard into play. When used correctly you wipe your opponent’s board, while also placing a large number of powerful creatures into play under your command.
If you enjoyed this deck you should check out my Blue White Living End Deck