Halana and Alena are a huge target and likely wont stick around for long on the battlefield, but if youre able to untap with them and play another creature after them, that creature gets an upgrade
The effect to make a creature unblockable comes up as well when combined with cards that grow in stats when you cycle a card
The distinction between AAA, AA, and A-Rank is usually very subtle, and what makes these cards special is that they often serve an important role in multiple formats without becoming a dominant part of the format
Your opponents might not want to waste valuable removal on something that doesnt make mana, but that just allows The Ooze to keep its secrets until the best moment
Simic Growth Chamber
That's why Upheaval is such a bomb: there are virtually no ways to deal with it, and once it is cast you can end up with two to three creatures plus a land on the board while your opponent literally has nothing, and has a hand full of sixteen cards they need to discard down to seven