Premature Burial

Pay 800 Life Points. Select 1 monster from your Graveyard, Special Summon it on the field in face-up Attack Position, and equip it with this card. When this card is destroyed, destroy the equipped monster.

This cad can summon most Monsters from the Graveyard. However, there are rules and exceptions. Take the Dark Magician. Even if it was discarded to the Graveyard by a Card Effect, it can still be Special Summoned. However, if you discard a Monster that has special Summoning conditions (such as the Red Eyes Darkness Dragon, or the Gate Guardian), without having Summoning it using it's special conditions, that Monster may not be summoned from the Graveyard. However, if it was summoned, and then destroyed in battle, or by a card effect, it can be Summoned then from the Graveyard.