Death from above

As additional cost to play Death from above,
pay half of your life rounded down.
Destroy all of the creatures into play of
each player. They can't be regenerated.
Any land becomes a swamp and lose any type
and all ability, exept mana's abilities.
(Any land can produce only black mana)
(Look at my works, ye mighties.. And despair!
— David, human replicant)