Regarding Chandra's Embercat, if by "block the stack" you mean prompts you for priority for its mana ability, it is a bug that should be fixed when Historic Anthology 3 goes live. We want to prompt you for priority for mana abilities with a side effect, like The Great Henge's, and abilities with mana that can be spent for two different types of costs accidentally got caught up in the logic for that.
As for Risen Reef, you have to remember that 99% of our rules-text code is machine-generated from the text of rule, in English. Risen Reef reads "look at the top card of your library. If it’s a land card, you may put it onto the battlefield tapped. If you don’t put the card onto the battlefield, put it into your hand." That is literally broken into 25 steps, branches, and labels, which look a little like the following (I took some out for brevity):
- Look at the top card of your library (this pops up that "Seen Cards" interface)
- Check if it's a land card, i...
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