You don't want to be a threat in the early game, as you need time to set up to be able to cast your haymaker 8+ mana cards
For example, you could put it onto the battlefield with Chord of Calling, it could be countered by Essence Scatter (but not by Negate), and opponents couldn't make you discard it with Duress
Yuna, Hope of Spira appears not only in several Domain Overlords decks but also as the centerpiece of new Bant Omniscience and Naya Enchantment decks
It's a special ability that doesn't use the stack, though using a morph ability often causes abilities to trigger that will use the stack
Check your local game stores and select Disney parks and stores from Friday, 7th March, then larger retail stores and online from Friday 21st, Match
Activated and triggered abilities are everywhere in modern Magic, and this lets you get more out of all of them