When this card on the field is destroyed and sent to the Graveyard: You can add 1 Union monster from your Deck to your hand. Once per turn, you can either: Target 1 Machine-Type monster you control; equip this card to that target, OR: Unequip this card and Special Summon it in face-up Attack Position. (A monster can only by equipped with 1 Union monster at a time. If the equipped monster would be destroyed, destroy this card instead.)
"Machine Duplication", can help you summon 3 copies of Peacekeeper from your deck to the field, once all of them are destroyed you can search up to 3 Union monsters from your deck, or even most of A-Z monsters.
Equips self from field / Adds from Deck to hand
Redirects destruction / Destroys itself
Special Summons itself from your Spell & Trap Card Zone