Boonweaver Giant from Magic 2015 is a functionally better version of Auratouched Mage. He gets to search your graveyard, hand, and/or library for an Aura card, then you put it on him. Even though he’s 7 mana, which is one more than Auratouched Mage, he can search more places. He’s also a 4/4, so he’s a bit tougher than his predecessor. The downside is that, unlike Auratouched Mage, if he’s removed from the board before that Aura can be attached to him, the Aura simply goes to the graveyard. So, he’s both better and worse.
Of course, if you play either of these cards, or both, alongside a Commander like Bruna, Light of Alabaster, this won’t matter. Bruna doesn’t care where your Auras are, whether they’re in your hand, in your graveyard, or attached to one of your other creatures. So while Auratouched Mage may be better about ensuring a card ends up in your possession no matter what, Bruna’s not going to care as long as you got that powerful Aura (say, Eldrazi Conscription, Corrupted Conscience, or Celestial Mantle) out of the library and into a place where she can grab it. If you’re playing a deck like Zur the Enchanter or Krond the Dawn-Clad, however, Boonweaver Giant getting killed is a bit more unfortunate. At least you get the Aura out of the library.
Boonweaver Giant is never going to see play outside of Commander. Seven mana is just too much for a card that’s little more than a tutor in pretty much any other format. Heliod’s Pilgrim at common is much more cost-effective. In fact, the Pilgrim is even better alongside Bruna than this Giant. The Pilgrim is better in Zur and Krond, as well. Boonweaver Giant has definitely been included in Bruna decks over time, but that deck doesn’t play a lot of creatures. To be honest, a 7 drop is a stretch when you already have Auratouched Mage and Sovereigns of Lost Alara at 6 mana each. It’s the tutoring effect that you care about, really. It’s still playable in more than a few Aura-happy decks, just for purposes of redundancy - a feature that’s important in Commander.
Unfortunately for the Giant, overall Auratouched Mage has continued to see far more play in Commander. Boonweaver Giant does see lots of play alongside Bruna, but even then, the Mage continues to supplant it as the more popular option. But, there is actually one deck that makes good use of Boonweaver Giant's services, and it's not one you'd necessarily expect: Karador, Ghost Chieftain!
In Karador, Ghost Chieftain, Boonweaver Giant is played alongside an Urza's Destiny enchantment called Pattern of Rebirth. There's a pretty sweet combo with these cards, along with Fiend Hunter and Reveillark. The combo is a little complex, but once you have it down, it's pretty awesome.
The Boonweaver Giant / Pattern of Rebirth Combo
First, you need to have a sacrifice outlet, such as Carrion Feeder or Viscera Seer, to sacrifice Boonweaver Giant to. Then, when Boonweaver enters play, you search out Pattern of Rebirth. So, what Pattern of Rebirth does:
When enchanted creature is put into a graveyard from play, that creature’s controller may search his or her library for a creature card and put that card into play. If that player does, he or she then shuffles his or her library.
With Pattern of Rebirth's ability, you find Karmic Guide. The Guide returns Boonweaver to play, then you get Pattern of Rebirth back attached to the Giant. Sacrifice Boonweaver again and search out Fiend Hunter. With Fiend Hunter's exile ability, you choose Karmic Guide.
You then sacrifice Fiend Hunter to bring Karmic Guide back into play. You use the Guide to get Boonweaver back, as well as Pattern of Rebirth. This time, you sacrifice Boonweaver to use Pattern's ability to find Reveillark. Then, sacrifice Karmic Guide, then Reveillark, which can return both Karmic Guide and Fiend Hunter to play. Use the Karmic Guide to get back Boonweaver and use Fiend Hunter to exile Karmic Guide again.
Now, you can sacrifice Boonweaver to get any creature from your deck. Then, sacrifice Fiend Hunter to return Karmic Guide again, which will bring back Reveillark. You repeat the cycle until you bring out whatever creatures you need for game winning combos from your deck. If no one stops the combo, you pretty much just win the game. Basically you're hoping to get a couple of infinite pairs on the board with something like Altar of Dementia or Blood Artist in play. There's a whole bunch of things you can do with this sort of Karador combo deck.
Here's a guide to the Karador Boonweaver/Pattern of Rebirth Combo.
So, while Boonweaver Giant doesn't actually win you the game, per se, he helps you greatly in assembling combo pieces. He's pretty darn useful in the deck!
Also, Gift of Immortality is pretty useful with Boonweaver Giant, as well. There are some silly things you can do with it. Albeit, they're nowhere as good as the combo with Pattern of Rebirth, but they certainly exist.
Really, Boonweaver Giant is a pretty solid card, but being seven mana, it takes a really particular deck, like Karador, to use him to his fullest potential. I'd argue he's pretty good in any Abzan (green/white/black) deck that can run those cards mentioned in the Pattern of Rebirth combo, although Karador is typically the Commander you'd want to run with that sort of strategy. He's a pretty cool card and definitely one that can help you win games in EDH with Karador!
He's also not bad in Bruna, Light of Alabaster EDH decks, either. That I can tell you with experience!