Think of it like your own personal Jace's Archivist, but you get to offload a bunch of the cards you discarded directly into play
If you cast an instant spell before Kalamax becomes tapped, its first ability won't trigger when you cast your second
You can't play Wrenn and One during another player's turn, and you can't play Wrenn and One if you don't have any land plays remaining
Discarding your hand often doesnt matter with cards like Yawgmoth's Will, and occasionally it even becomes a boon with cards like Infernal Tutor and Echo of Eons
Especially if your card came with a lot of other cards, its possible to tear the cardor a cheap card that came along with it, like a common card or a basic energy cardand look to see if the card is authentic
And you really don't need yet another Counterspell, do you