Root Cage {1}{G}
Enchantment
Mercenaries don't untap during their controllers' untap steps.
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Cards that do something similar expected a card that isn't here?
Reports become test cases the matcher is graded against before an update ships. Delvefall isn't a chatbot guessing, it compares the printed rules text of every card with plain math, and examples like yours decide which differences should count.
The Blackstaff of Waterdeep 80%
$0.20#19806
"You may choose not to untap this card during your untap step."
Ashnod's Battle Gear 80%
$0.20#30335
"You may choose not to untap this artifact during your untap step."
Vedalken Shackles 80%
$7.66#11447
"You may choose not to untap this artifact during your untap step."
Deserter's Quarters 80%
$0.05#29280
"You may choose not to untap this artifact during your untap step."
Helm of Possession 80%
$5.07#14749
"You may choose not to untap this artifact during your untap step."
Damping Field 80%
$8.60#27078
"Players can't untap more than one artifact during their untap steps."