Blackblade Reforged
Legendary Artifact — Equipment
Equipped creature gets +1/+1 for each land you control.
Equip legendary creature 
Equip 
"Tempered in the blood of ten thousand sacrifices? Superstitious drivel." —Mishra, note to his researchers
Chris Rahn
Rulings
Whether the target creature is legendary is checked only as Blackblade Reforged's first equip ability is activated and as that ability resolves. If the creature somehow becomes nonlegendary later, Blackblade Reforged remains attached to it.
(wotc • 2018-04-27)
"Equip [quality] creature" is a variant of the equip keyword. "Equip [quality] creature [cost]" means "[Cost]: Attach this Equipment to target [quality] creature you control. Activate only as a sorcery."
(wotc • 2018-04-27)
Printings
Rulings
Whether the target creature is legendary is checked only as Blackblade Reforged's first equip ability is activated and as that ability resolves. If the creature somehow becomes nonlegendary later, Blackblade Reforged remains attached to it.
(wotc • 2018-04-27)
"Equip [quality] creature" is a variant of the equip keyword. "Equip [quality] creature [cost]" means "[Cost]: Attach this Equipment to target [quality] creature you control. Activate only as a sorcery."
(wotc • 2018-04-27)