The very last game of magic I played I used this to make a turn 3 Verdurous Gearhulk and grew my Devoted Druid back up
Even when we aren't comboing off, Mirrorpool gives us some odd value by copying Manic Scribe (especially in the late game when we have delirium) for additional milling, or sometimes just copying a Compelling Argument is enough to get our opponent out of cards
High risk in that getting it killed results in no extra cards and not getting it killed might result in your taking too much damage
Cards like Agents Toolkit can help make sure Blue and your squad end up with Shield counters, which are great at protecting your team from board wipes
Flare of Cultivation Flare of Cultivation is basically Cultivate 80% of the time, but being able to sacrifice a green creature to cast this for free is nothing to scoff at
That will fit a lot of decks, but what happens in the next chapter is that you get two rounds of a pseudo Council's Judgment, and that's a pretty strong effect