Lightning Greaves
Artifact — Equipment
Equipped creature has [[ keyword: "haste" ]] and shroud.
Equip 
When you spend most of your time running for your life, it pays to invest in quality footwear.
Adrián Rodríguez Pérez
Rulings
You can't simply unequip Equipment from a creature. If Lightning Greaves is attached to the only creature you control, you won't be able to attach other equipment to it (or target it with anything else) until you have another creature onto which you can move Lightning Greaves.
(wotc • 2020-08-07)
If a creature enters the battlefield under your control and gains haste, but then loses it before attacking, it won't be able to attack that turn. This means that you can't use one Lightning Greaves to allow two new creatures to attack in the same turn.
(wotc • 2020-08-07)
Rulings
You can't simply unequip Equipment from a creature. If Lightning Greaves is attached to the only creature you control, you won't be able to attach other equipment to it (or target it with anything else) until you have another creature onto which you can move Lightning Greaves.
(wotc • 2020-08-07)
If a creature enters the battlefield under your control and gains haste, but then loses it before attacking, it won't be able to attack that turn. This means that you can't use one Lightning Greaves to allow two new creatures to attack in the same turn.
(wotc • 2020-08-07)