Mana Vault 
Artifact
This artifact doesn't untap during your untap step.
At the beginning of your upkeep, you may pay {4}. If you do, untap this artifact.
At the beginning of your draw step, if this artifact is tapped, it deals 1 damage to you.
{T}: Add {C}{C}{C}.
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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.
Grim Monolith 100%
$472.34#674
"This artifact doesn't untap during your untap step."
+2 more matching lines
Basalt Monolith 100%
$3.75#561
"This artifact doesn't untap during your untap step."
+2 more matching lines
Elaborate Firecannon 100%
$0.05#28481
"This artifact doesn't untap during your untap step."
+1 more matching line
Ashnod's Battle Gear 95%
$0.20#30335
"You may choose not to untap this artifact during your untap step."
Vedalken Shackles 95%
$7.66#11447
"You may choose not to untap this artifact during your untap step."
Deserter's Quarters 95%
$0.05#29280
"You may choose not to untap this artifact during your untap step."
Helm of Possession 95%
$5.07#14749
"You may choose not to untap this artifact during your untap step."