Offering some cross-tribal benefits for assassins, mercenaries, and rogues, Mari seems like an excellent support card for Etrata, the Silencer due to her ability to exile enemy creatures with hit counters on them when they die
Yes, you lose some life every turn, but The One Ring is also indestructible, making it extremely difficult for your opponents to interact with, and you really should have some bounce spells to maximise the potential of The One Ring (and to not lose too much life)
Throw in that surprisingly solid parting shot death trigger, and Moonveil Regent punches well above its financial weight in 2026
When it enters, it picks an enemy creature and everything else gets -2/-2 to set up a one-on-one showdown
Four power is utterly huge
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as a flashback cost), add any cost increases (such as kicker costs), then apply any cost reductions (such as that of Urianger Augurelt's last ability)