Repository Skaab is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Exploit (When this creature enters, you may sacrifice a creature.) When this creature exploits a creature, return target instant or sorcery card from your graveyard to your hand.

Complete guide

Repository Skaab is a versatile blue creature that turns your board presence into powerful graveyard recursion. By utilizing the Exploit keyword, this Zombie allows you to trade a creature for a high-impact spell already cast earlier in the game.

Understanding Exploit

Repository Skaab features two distinct triggered abilities. The first is Exploit, which triggers when the Skaab enters the battlefield, allowing you to sacrifice a creature. The second is a 'When this creature exploits a creature' ability, which only triggers if you actually choose to sacrifice a creature to the first ability.

The Step-by-Step Resolution

When Repository Skaab enters, the Exploit ability is put on the stack. You do not choose which creature to sacrifice or which spell to target yet. As the Exploit ability resolves, you choose whether to sacrifice a creature. If you do, the second ability triggers immediately. At this point, you must choose a target instant or sorcery card in your graveyard. That target is then returned to your hand when the second ability resolves.

Common Pitfalls

A common mistake is trying to sacrifice the same creature to multiple Exploit triggers; you can only sacrifice one creature per Exploit trigger. However, Repository Skaab can sacrifice itself to its own Exploit ability. If it does, its second ability will still trigger, and you will successfully return a spell to your hand even though the Skaab is no longer on the battlefield.

When to Cast It

This card is best used when your graveyard is stocked with powerful spells and your board has 'death triggers.' Since the Exploit keyword provides a sacrifice outlet, it is an excellent way to trigger abilities that occur when a creature dies while simultaneously recovering resources.

Interaction examples

Maximizing Value with Solemn Simulacrum

Solemn Simulacrum

With Solemn Simulacrum on the battlefield, you cast Repository Skaab. When the Skaab enters, you use the Exploit ability to sacrifice Solemn Simulacrum. This triggers two abilities: the Skaab's recursion ability and the Simulacrum's death trigger. You will draw a card from the Simulacrum and return an instant or sorcery to your hand from the Skaab.

Doubling Up with Roaming Throne

Roaming Throne

If you control Roaming Throne with 'Zombie' chosen as the creature type, Repository Skaab's abilities will trigger an additional time. When the Skaab enters, you get two Exploit triggers. If you sacrifice a creature to the first trigger, the 'When this creature exploits' ability triggers twice. You can then sacrifice a second creature to the second Exploit trigger to get two more recursion triggers, potentially returning four spells to your hand.

Self-Sacrifice for Spells

If you have no other creatures, you can cast Repository Skaab and choose to sacrifice the Skaab itself to its own Exploit trigger. Even though the Skaab is put into the graveyard, its 'When this creature exploits a creature' ability triggers, allowing you to return an instant or sorcery card to your hand.

Guide written with AI from the official text and rulings. Official English text prevails.