I have Dack's Duplicate on the field, copying nothing, kept alive by Glorious Anthem. I play a Clone, choosing to copy the Duplicate. Now it has the Duplicate's replacement effect; can I, with that, choose to copy the Duplicate again, and then the Duplicate again, etc. an arbitrary number of times before eventually choosing to copy nothing–resulting in a 1/1 (because of the Anthem) with arbitrarily many copies of haste and dethrone?

The underlying question: Does this situation represent one Duplicate copy ability trying to replace the same event (the Clone's eventual entrance) over and over, or does each instance of choosing a Duplicate create a new replacement effect which is free to replace the entrance event an additional time?

Edit: The underlyinger question, after some discussion: If the creature I already have entering the battlefield has the DD ability, and by using it to copy something with the DD ability I create another instance of that replacement effect, does that one replace the entire modified enters-the-battlefield event, including the “except it gains haste and dethrone” part, or does it only replace the actual entering part, leaving the rest of the previous modification (the “except it gains haste and dethrone”) part intact?

Edited Finn Ellis (May 15, 2016 12:13:14 PM)

No, you can't get arbitrarily many instances of haste and/or dethrone this way.

Dack's Duplicate adds haste and dethrone to itself as part of applying its copy effect. If you then apply another copy effect to the Duplicate, those abilities are overwritten by the new copy effect, just like all the creature's other characteristics. Each time you apply the Duplicate's replacement you wipe away the previous instance of haste and dethrone and replace them with new instances, so you'll only ever end up with one instance of each.

Edited Callum Milne (May 15, 2016 02:44:53 PM)