How to beat the first challenge mode *spoiler warning*

Yeah, I finally worked my way through it. I started attempting it with different decks and kept running into speed/consistency problems, and eventually made a dedicated hoser deck since a lot of the opponents can be shut down by just one card.
What I started with was a Tooth and Nail type deck, backed by Moat and its creature counterpart, Magus of the Moat. The goal was to get Platinum Angel out, since there are very few answers to it in the first challenge. I started with Progenitus as a finisher, but came to realize that mister "protection from everything" couldn't fly over the Moat. So rather quickly, he was swapped out for Iridescent Angel, who is just as hard to block (no deck contains a flying artifact creature, although the faeries can steal your Platinum Angel to block with).
But the Tooths were too slow, and once I came to realize I was trying to use a 9 mana sorcery to bring out 7 mana angels, I changed them out for Oath of Druids, which is better. But then the Birds of Paradise had to go because I was oathing them into play, along with all the Urzatron mess. After revamping the mana base and acceleration spells, I sped the deck up. I was also able to splash blue for Tinker and threw some Lightning Greaves for that added protection.
Now with the Oath working, I did some more tweaking. The last big change was to remove Magus of the Moat, since I realized I was consistent enough to rely on Platinums instead and the Magus was a bad Oath pull in certain matchups. I removed them and instead put in two Eternal Witnesses, a Timetwister to help curb a decking problem, and a Demonic Tutor to help speed things up.
So that leaves me with the final product, which eventually cleared the first challenge.
4x Platinum Angel
1x Iridescent Angel
2x Eternal Witness
4x Moat
4x Oath of Druids
1x Tinker
1x Time Walk
1x Timetwister
1x Ancestral Recall
1x Demonic Tutor
2x Naturalize
2x Lightning Greaves
4x Land Grant
4x Fertile Ground
5x Moxes
1x Black Lotus
1x Sol Ring
4x Savannah
4x Temple Garden
4x Tropical Island
4x Tundra
1x Bayou
4x Forbidden Orchard
Now for some briefings of the matchup!
Round 1- Kobolds
Not too much of a problem since they aren't paticularly powerful. Moat shuts them down, although the Lighting Bolts can finish you off if you've taken too much damage already. Platinum Angel usually wins, but again, they can be double bolted, but with a Greaves equipped is a guarenteed win. No flyers to block with, so yeah.
Round 2- Zombies
This deck is FAST due to the +2/+1 of the Warchief and the lesser cost, combined with Dark Rituals. But with no flying or targetted removal whatsoever, Moat/Platinum alone is game. Heck, you don't even need a finisher because they'll likely Graveborn Muse themselves to death.
Round 3- Faeries
This is troublesome. Moat is worthless here, and a sole Platinum is susceptable to Control Magic. There's also a stray counter or two. Thankfully, they will kill themsevles with Bitterblossom, and if a Platinum resolves and gets Greaves, it's the same as above. Iridescent can help with finishing, but if a Platinum is stolen, it can be blocked and killed.
Round 4- Kithkin (I may start screwing up order around here somewhere)
Possible flyers in Spectral Procession, Cloudgoat Ranger, and a fully evolved Figure of Destiny, so Moat alone is not a lock, and Platinums can be blocked. An early Moat is still a safe bet, and Platinum will make you unkillable until Iridescent finishes.
Round 5- Merfolk
Again with the counterspells, but heavier this time and backed by "comes into play, draw a card" Merfolk. But no flyers/other damage or permanent targetting, so a resolved Moat/Platinum is game. Be warned, however, that while Moat is an eventual win, too many counterspells can draw out the game long enough to force a crash.
Round 6- Relentless Rats
Same as the zombies, fast with Rituals, but so straightforward a single Moat/Platinum wins and has no disruption isses at all.
Round 7- Elves
Other than Worship (that and the faeries' Control Magic are the reasons for the Naturalize), it's the same as the zombies/rats. Watch out for crashes, however, because elves can produce TONS of mana, tons more elves, then use Collective Unconscious.
Round 8- Goblins
These are actually pretty meh, despite the potential. The AI fails to play most of them pre-combat despite the Chieftan giving free haste. Again with the lack of flyers, but be cautious that the Seige-Gang Commander can fling goblins past the Moat and even kill un-Greaves'd Platinums.
Round 9- Solders
Starting with a 3/3 and three 2/2's means you must may find yourself mulliganing aggressively. With Honor of the Pure ramping up the starting lineup's power from 7 to 13, you likely will not last through two combat phases. However, if you do get that turn 1 Oath that pulls a Platinum or turn 2 Tinker/Moat, the game is yours.
Round 10- Slivers
With 7 starting power you're dead in 3 hits, although the deck does not kill in 2 swings as much as the Soldiers tend to. The only real issue now is that Winged Sliver can render Moat useless, but if you're lucky enough not to see one early, it can buy some time. I'm not completely sure if there's an answer to Platinum, but I don't think there is. And actually, there may be an issue with colorless flying Slivers being able to block Iridescent, but hopefully you can Oath out angels before that's a problem.
What I started with was a Tooth and Nail type deck, backed by Moat and its creature counterpart, Magus of the Moat. The goal was to get Platinum Angel out, since there are very few answers to it in the first challenge. I started with Progenitus as a finisher, but came to realize that mister "protection from everything" couldn't fly over the Moat. So rather quickly, he was swapped out for Iridescent Angel, who is just as hard to block (no deck contains a flying artifact creature, although the faeries can steal your Platinum Angel to block with).
But the Tooths were too slow, and once I came to realize I was trying to use a 9 mana sorcery to bring out 7 mana angels, I changed them out for Oath of Druids, which is better. But then the Birds of Paradise had to go because I was oathing them into play, along with all the Urzatron mess. After revamping the mana base and acceleration spells, I sped the deck up. I was also able to splash blue for Tinker and threw some Lightning Greaves for that added protection.
Now with the Oath working, I did some more tweaking. The last big change was to remove Magus of the Moat, since I realized I was consistent enough to rely on Platinums instead and the Magus was a bad Oath pull in certain matchups. I removed them and instead put in two Eternal Witnesses, a Timetwister to help curb a decking problem, and a Demonic Tutor to help speed things up.
So that leaves me with the final product, which eventually cleared the first challenge.
4x Platinum Angel
1x Iridescent Angel
2x Eternal Witness
4x Moat
4x Oath of Druids
1x Tinker
1x Time Walk
1x Timetwister
1x Ancestral Recall
1x Demonic Tutor
2x Naturalize
2x Lightning Greaves
4x Land Grant
4x Fertile Ground
5x Moxes
1x Black Lotus
1x Sol Ring
4x Savannah
4x Temple Garden
4x Tropical Island
4x Tundra
1x Bayou
4x Forbidden Orchard
Now for some briefings of the matchup!
Round 1- Kobolds
Not too much of a problem since they aren't paticularly powerful. Moat shuts them down, although the Lighting Bolts can finish you off if you've taken too much damage already. Platinum Angel usually wins, but again, they can be double bolted, but with a Greaves equipped is a guarenteed win. No flyers to block with, so yeah.
Round 2- Zombies
This deck is FAST due to the +2/+1 of the Warchief and the lesser cost, combined with Dark Rituals. But with no flying or targetted removal whatsoever, Moat/Platinum alone is game. Heck, you don't even need a finisher because they'll likely Graveborn Muse themselves to death.
Round 3- Faeries
This is troublesome. Moat is worthless here, and a sole Platinum is susceptable to Control Magic. There's also a stray counter or two. Thankfully, they will kill themsevles with Bitterblossom, and if a Platinum resolves and gets Greaves, it's the same as above. Iridescent can help with finishing, but if a Platinum is stolen, it can be blocked and killed.
Round 4- Kithkin (I may start screwing up order around here somewhere)
Possible flyers in Spectral Procession, Cloudgoat Ranger, and a fully evolved Figure of Destiny, so Moat alone is not a lock, and Platinums can be blocked. An early Moat is still a safe bet, and Platinum will make you unkillable until Iridescent finishes.
Round 5- Merfolk
Again with the counterspells, but heavier this time and backed by "comes into play, draw a card" Merfolk. But no flyers/other damage or permanent targetting, so a resolved Moat/Platinum is game. Be warned, however, that while Moat is an eventual win, too many counterspells can draw out the game long enough to force a crash.
Round 6- Relentless Rats
Same as the zombies, fast with Rituals, but so straightforward a single Moat/Platinum wins and has no disruption isses at all.
Round 7- Elves
Other than Worship (that and the faeries' Control Magic are the reasons for the Naturalize), it's the same as the zombies/rats. Watch out for crashes, however, because elves can produce TONS of mana, tons more elves, then use Collective Unconscious.
Round 8- Goblins
These are actually pretty meh, despite the potential. The AI fails to play most of them pre-combat despite the Chieftan giving free haste. Again with the lack of flyers, but be cautious that the Seige-Gang Commander can fling goblins past the Moat and even kill un-Greaves'd Platinums.
Round 9- Solders
Starting with a 3/3 and three 2/2's means you must may find yourself mulliganing aggressively. With Honor of the Pure ramping up the starting lineup's power from 7 to 13, you likely will not last through two combat phases. However, if you do get that turn 1 Oath that pulls a Platinum or turn 2 Tinker/Moat, the game is yours.
Round 10- Slivers
With 7 starting power you're dead in 3 hits, although the deck does not kill in 2 swings as much as the Soldiers tend to. The only real issue now is that Winged Sliver can render Moat useless, but if you're lucky enough not to see one early, it can buy some time. I'm not completely sure if there's an answer to Platinum, but I don't think there is. And actually, there may be an issue with colorless flying Slivers being able to block Iridescent, but hopefully you can Oath out angels before that's a problem.