https://www.reddit.com/r/ModernMagic/comments/3re78d/sideboarding_with_amulet_bloom_xpost_from_rspikes/

Common Sideboarding Options

    Leyline of Sanctity: I think this is one of the most important cards in the sideboard. Most lists that I have seen run 1 - 3. From my experience running 3 is correct. It is a live card in many matchup's ranging from amazing, to okay. Sometimes these feel like wasted sideboard slots, but trust me, they are a beating against a lot of the meta. Running 3 gives you a very good chance of seeing it in the an opener.

    Decks it's good against: G/B/x, Ad Nauseum, Latern Control, Burn, any deck trying to use Gifts Ungiven.

    Ghost Quarter: This is usually a common sideboard slot as a one of. It hedges you in the mirror, and is good at killing pesky Inkmoth Nexus. I think if you play on of these main, that it isn't worth the sideboard slot, 2 only becomes very good against the mirror. Also, allows you to Ghost Quarter your own land to find your forest if you need to.

    Decks it's good against: Bloom Titan, Jund, Affinity, Infect.

    Forest: I think the 2nd copy of Forest in the sideboard is very good. I always side it in against Blood Moon decks, and decks running Path to Exile. It allows you to cast your Primeval Titan under a Blood Moon, and gives you a better chance at having a basic land to cast Seal of Primodium or Nature's Claim.

    Decks it's good against: Any deck running Blood Moon (Affinity, Splinter Twin, Blue Moon, Jund), UWR Control, GW Hatebears, Collected Company.

    Seal of Primordium: This is one of two cards that you 100% have to run in the sideboard, just to the fact you can very rarely win under a resolved Blood Moon. It's good because you don't have to leave open mana, and you can just sit on it, its bad because of the card Spell Snare. Many times playing the deck, I have lost to Remand/Spell Snare your Seal, untap Blood Moon. It sucks, but it happens. I usually like to run more of these than Nature's Claim, but I like the mix of the two. Also good against Affinity allowing you to live longer, I usually board it in against Infect as well, as it hits Inkmoth and Spellskite.

    Decks it's good against: Bloodmoon decks, Affinity, and Infect.

    Nature's Claim: On the other hand this card can be very good, and very bad as well. That is why I like the mix. This card is nice because you can just float mana in reponse to a Blood Moon and kill it. Although, it gets hit by Dispel which sucks, and you have to leave open the mana (which can slow what you want to do down). Again good against Affinity and Infect as well.

    Decks it's good against: Same as above.

    Thragtusk: Thragtusk is amazing. I've seen anywhere from 0 - 3 copies of this guy in the SB's. As of right now I play 3. He is a value creature to ramp into. He gains you life. He doesn't give opponents who play Path to Exile all of the value. You're Jund/Junk opponent has to spend 2 spells to kill him. I think he is worth playing 1 - 2 in almost every list.

    Decks it's good against: G/B/x, UWR Control, Burn, Zoo, GW Hatebears.

    Sigarda, Host of Herons: This card is a weird one, almost everyone seems to play it, but it has never been good for me. It seems like a Silver Bullet against Jund/Junk, but seemingly useless almost everywhere else. If your Meta is full of Jund/Junk play this. If not, don't.

    Decks it's good against: Jund/Junk.

    Hornet Queen: Now this card right here has been one of my favorite in the SB for a long time. It is a trump card in so many matchups, most decks cannot defeat a resolved Hornet Queen without getting 1 for 5ed.

    Decks it's good against: Living End, Zoo, Merfolk, Jund/Junk. (This card sucks against Elves, I learned this the hard way. RTFC)

    Engineered Explosives: Again this is a one of that I have seen in some lists. I love this card. I used to run 3 Pyroclasm in the SB, but I cut one for this. It is a Pseudo Pyroclasm, that is easier to find, and better in certain match-ups. Finding it off of Ancient Stirrings/Tolaria west is awesome. And you can reasonably get it to 5. Also a small hedge against Blood Moon.

    Decks it's good against: Merfolk, Affinity, Infect, Boggles.

    Pyroclasm - This card is meh. I do believe you have to run it, and I do not believe that Firespout is better. Pyroclasm makes your Affinity, Elves, Burn, and Infect matchup a ton better. And Firespout can be a turn too slow. I recommend 1 or 2.

    Decks it's good against: Infect, Burn, Affinity, Elves.

    Swan Song: This card used to be played a lot more than it is now. Personally, I love this card. But it's not necessary. For me, I love it against Splinter Twin, the Mirror, and other random Combo decks like UR Storm, and Ad Nauseum.

    Decks it's good against: UR Storm, Twin, Bloom Titan.

    Chalice of the Void: This card is interesting. It has always seemed to hurt our own deck more than others. I like it against Remand/Path decks, as those are problematic cards. It's quite slow, but can be easily found with Stirrings or Tolaria West.

    Decks it's good against: Twin, Boggles, UR Storm, Suicide Zoo?

    Inferno Titan: This is a card that a few of other Bloom players in my area have experimented with. It's insane against Blood Moon decks, and decks like Jund. It seems spicy, but at cutting what from the SB? If anyone has more opinions on this card i'd love to hear it.

    Decks it's good against: Twin, Blue Moon, Jund, Zoo.

    Ugin, the Spirit Dragon: This card is a late game trump. It comes down and can rarely be killed. Although he seems sort of hard to cast, I like the idea of playing this card, you can play in through Blood Moon, and go even more over the top of other creature decks.

    Decks it's good against: Jund, Junk, Elves, Zoo.

    Ruric Thar, the Unbowed: A lot of original lists played this guy. I think he was a lot better when UR Cruise Delver was a deck because he couldn't really ever be killed. I am not sure how I feel about him currently, seems like a KO against Twin or UR Storm though.

    Decks it's good against: UR Storm, Twin, maybe Grixis Delver?