Does damping sphere shut down nyxbloom ancient? I read somewhere that it don't but I'm trying to prove to a friend he's mistaken. even MTGO online damping sphere don't stop it. so is this correct?
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If you control Nyxbloom Ancient, Damping Sphere is on the battlefield, and you tap a land you control for—
exactly one mana, it produces C instead of any other type and amount.
two or more mana, it produces either C or CCC instead of any other type and amount, your choice (C.R. 616.1, 616.1d-e, 616.2).
This is because Nyxbloom Ancient's effect replaces the amount of mana the land would otherwise produce when it's tapped for mana. Damping Sphere, however, applies only if the land would produce more than one mana, so that in the first case above, Nyxbloom Ancient changes the one mana to three, then Damping Sphere kicks in and changes the three mana to C (C.R. 616.2).
(Compare Nyxbloom Ancient with Wild Growth, which doesn't add to the amount of mana the enchanted land would produce when tapped for mana, since it's a triggered ability from Wild Growth [C.R. 603.1], rather than a replacement effect.)
Note that Damping Sphere's first ability doesn't apply to nonland permanents, so that despite Damping Sphere, if you control Nyxbloom Ancient and tap a nonland permanent for mana, it will still produce three times as much mana as usual and that mana's type remains unchanged.
then why On Magic online lands still produce 3x the amount even with damping sphere out?
If Damping Sphere is on the battlefield, and you control Nyxbloom Ancient, and a land you control nevertheless produces three times as much mana when you tap it for exactly one mana, then that is a bug in Magic Online.
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-MadMage
If you control Nyxbloom Ancient, Damping Sphere is on the battlefield, and you tap a land you control for—
(Compare Nyxbloom Ancient with Wild Growth, which doesn't add to the amount of mana the enchanted land would produce when tapped for mana, since it's a triggered ability from Wild Growth [C.R. 603.1], rather than a replacement effect.)
Note that Damping Sphere's first ability doesn't apply to nonland permanents, so that despite Damping Sphere, if you control Nyxbloom Ancient and tap a nonland permanent for mana, it will still produce three times as much mana as usual and that mana's type remains unchanged.
EDIT (Feb. 21): Correctness edit.
EDIT (Aug. 26): Correctness edit.