Ink-Treader: This feels like a Modern Horizons card. Probably too strong for a Standard in which lands with the land types exist, but feels right at home in an Aristocrats deck. Did you intend for the card to be able to return the same land that was sacrificed?
marioguy3 "Red instant or sorcery
spell". Additionally, I'm not really on board with a card that is effectively a do-nothing unless you're also in red. It should probably have some kind of effect that is usable in just mono-black (yes hybrid exists, I know.) I could see this affecting black and red spells and still being fine.
slimytrout: Probably would have went with flying instead of hexproof on the final ability - hexproof to effectively your entire team just by holding up U every turn. I like how this is playable in any color identity besides green. There is an argument that effects like Prismatic Omen allow access to all of your card's abilities in mono-green but that's fine.
Subject16: A build-around for sure. Protects itself indefinitely with any white permanent that can be sacrificed to save a permanent from something. A bit obnoxious but I don't think it's too overpowered. If it could be a commander, maybe?
netn10: Seems like something you would only see in a Commander product or a Masters-type product, but man does this look fun to put in nearly any deck in its colors. I'd like to see a life cost attached to the recursion, though - you can effectively cheat some really big spells this way, and it protects itself with every piece of countermagic you play. Might be a bit over the top as is.
Lorn Asbord Schutta: I like the idea behind this card but I don't like that the discard is mandatory, especially since it seems like the discard is not intended to be a drawback. Neither one of these triggers should be mandatory.
spacemonaut: On a 3/3 for 5, I think this is balanced. Seems like it can take over the board in a hurry, but it feels very bad if removed. This effect reminds me a little bit of
Grave Betrayal but at a less prohibitive cost.
1) slimytrout
2) Ink-Treader
3) netn10