In the early days, decking was a win condition for decks that prevented anything from happening
You may activate each of those abilities only once each turn
Im happy to talk about the math and my methods in the comments here, on Twitter, but especially in the ProTrader Discord
This can be a little confusingespecially since The One Ring is probably one of the most dominant constructed cards of all time, but the two have nothing to do with one another
That ability is "when the last defense counter is removed from this permanent, exile it, then you may cast it transformed without paying its mana cost." This means that if for any reason a battle enters the battlefield without defense counters, it will be put into the graveyard and its controller will not get the chance to exile it
Athreos, God of Passage and Athreos, Shroud-Veiled are two different cards for the purposes of deckbuilding