If a targeted creature is already tapped when the spell resolves (and the spell mastery ability applies), that creature remains tapped and doesnt untap during its controllers next untap step
One of the hallmarks of a Spellslinger deck is the ability to copy spells
Damage doesn't reduce a creature's toughness, so that won't work, but a -X/-X effect or an accumulation of -1/-1 counters do the trick
And since those new nightbound transformation rules allow her to show up already transformed in most cases, this Arlinn feels much more like one of the pack
On top of that, it provides devotion for Gods like Iroas, God of Victory a cheeky little bonus
Svella, Ice Shaper Destroying all lands on the battlefield wont be an issue if you have other mana sources