Originally posted by Patrick Vorbroker:
Unmarked Origins checklist cards in a deck that can produce multiple colors of mana could feasibly be used to represent multiple cards, so they can't be allowed.
To me, this begs the question “If the decklist had 24 Islands as their only source of mana, would the infraction and penalty be the same?”
The IPG entry for D/DLP says for ambiguous names on the deck list that “needing to check the deck for confirmation is a sign that the entry is not obvious.” I believe that same logic applies for checklist cards - needing to check the rest of the deck for confirmation is a sign that this is not obvious. I'm going to re-use Riki's line of thinking here - if we let a player play with this hypothetical mono-blue deck, and their opponent plays turn 1 Thoughtsieze, if they called a judge over to ask what the checklist cards are we'd essentially have to confirm that not only are there no other flip walkers in the deck, but also that it's a mono-blue deck! It feels to me like allowing unmarked checklist cards at all, regardless of deck composition, should not be allowed - for logistical and practical reasons as well as for consistency.