Harbinger of the Seas causes all nonbasic lands to be Islands, and
Curse of Marit Lage prevents Islands from untapping during their controller's untap steps, nonbasic lands do not untap during their controller's untap steps.
Results
Nonbasic lands do not untap.
Mass Land Denial.
Metadata
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Bracket tag
RuthlessBracket 4+
For competitive decks at brackets 4+
1
2
3
4
5
1 · Exhibition5 · cEDH
Bracket tags are estimated from the cards and results of each combo, as a guideline rather than a strict classification.