I'd say, of the two-color combinations, BR is the most "discard your hand" happy. UB is all about "select things to be discarded" while BR is all about "just discard it all." Also, that's a good point on Lawkeeper's Ascension. Probably would need to change the quest counter trigger to countering spells.
Nephtakem's Leviathan7UU
Creature - Zombie Leviathan R
Nephtakem's Leviathan can't be countered.
Trample, islandwalk
Put the top three cards of your library into your graveyard: Return Nephtakem's Leviathan from your graveyard to the battlefield. Activate this ability only if you have fifteen or fewer cards in your library.
7/9
IIW: Lands which directly interact with win conditions, two examples would be (1) introducing new win conditions or (2) making it so that certain players can't win or lose.
Longpur, Who Hated the Sky3GG
Legendary Creature - Giant
Reach
As long as Longpur, Who Hated the Sky is on the battlefield or in your graveyard, creatures you control have reach.
Whenever a creature you control blocks a creature with flying, you may return Longpur from your graveyard to the battlefield.
4/5
Phoenix Cliffs
Land
Phoenix Cliffs enters the battlefield tapped. T: Add R to your mana pool. 4R: Return Phoenix Cliffs from your graveyard to the battlefield.
Drifting Gearscape
Land
Drifting Gearscape enters the battlefield tapped.
When Drifting Gearscape enters the battlefield, target artifact creature gets +1/+1 and gains flying until end of turn. T: Add C.
Basing this around the Ascension cycle from Zendikar
Lawkeeper AscensionWU
Enchantment R
Whenever an opponent casts a spell, you may put a quest counter on Lawkeeper Ascension.
As long as Lawkeeper Ascension has five or more quest counters on it, spells you opponents cast cost 1 more to cast.
Necromancer AscensionUB
Enchantment R
At the beginning of each end step, if you put a card from your graveyard into your hand or library this turn, you may put a quest counter on Necromancer Ascension.
At the beginning of your upkeep, if Necromancer Ascension has two or more quest counters on it, each player puts the top seven cards of his or her library into his or her graveyard.
Torturer AscensionBR
Enchantment R
At the beginning of each end step, if an opponent discarded a card this turn, you may put a quest counter on Torturer Ascension
As long as Torturer Ascension has three or more quest counters on it, each opponent's maximum hand size is reduced by seven.
Animist AscensionRG
Enchantment R
Whenever you play a land card, you may put a quest counter on Animist Ascension.
As long as Animist Ascension has five or more quest counters on it, lands you control are 3/3 Elemental creatures with haste and trample. They're still lands.
Prophet AscensionGW
Enchantment R
At the beginning of each end step, if your life total is greater than your starting life total, you may put a quest counter on Prophet Ascension.
As long as Prophet Ascension has ten or more quest counters on it, your life total cannot be reduced below your starting life total.
IIW: Lands which directly interact with win conditions, two examples would be (1) introducing new win conditions or (2) making it so that certain players can't win or lose.
Nephtakem's Leviathan 7UU
Creature - Zombie Leviathan R
Nephtakem's Leviathan can't be countered.
Trample, islandwalk
Put the top three cards of your library into your graveyard: Return Nephtakem's Leviathan from your graveyard to the battlefield. Activate this ability only if you have fifteen or fewer cards in your library.
7/9
IIW: Lands which directly interact with win conditions, two examples would be (1) introducing new win conditions or (2) making it so that certain players can't win or lose.
Longpur, Who Hated the Sky 3GG
Legendary Creature - Giant
Reach
As long as Longpur, Who Hated the Sky is on the battlefield or in your graveyard, creatures you control have reach.
Whenever a creature you control blocks a creature with flying, you may return Longpur from your graveyard to the battlefield.
4/5
Phoenix Cliffs
Land
Phoenix Cliffs enters the battlefield tapped.
T: Add R to your mana pool.
4R: Return Phoenix Cliffs from your graveyard to the battlefield.
Drifting Gearscape
Land
Drifting Gearscape enters the battlefield tapped.
When Drifting Gearscape enters the battlefield, target artifact creature gets +1/+1 and gains flying until end of turn.
T: Add C.
Mycosynth Generator + Golgari Guildgate
Decay Converter 3
Artifact
Decay Converter enters the battlefield tapped.
B, T, Pay 1 life: Create a 1/1 colorless Myr artifact creature token.
G, T, Pay 1 life: Add CCC.
Men or Monsters 1GG
Sorcery
An opponent chooses one —
Lawkeeper Ascension WU
Enchantment R
Whenever an opponent casts a spell, you may put a quest counter on Lawkeeper Ascension.
As long as Lawkeeper Ascension has five or more quest counters on it, spells you opponents cast cost 1 more to cast.
Necromancer Ascension UB
Enchantment R
At the beginning of each end step, if you put a card from your graveyard into your hand or library this turn, you may put a quest counter on Necromancer Ascension.
At the beginning of your upkeep, if Necromancer Ascension has two or more quest counters on it, each player puts the top seven cards of his or her library into his or her graveyard.
Torturer Ascension BR
Enchantment R
At the beginning of each end step, if an opponent discarded a card this turn, you may put a quest counter on Torturer Ascension
As long as Torturer Ascension has three or more quest counters on it, each opponent's maximum hand size is reduced by seven.
Animist Ascension RG
Enchantment R
Whenever you play a land card, you may put a quest counter on Animist Ascension.
As long as Animist Ascension has five or more quest counters on it, lands you control are 3/3 Elemental creatures with haste and trample. They're still lands.
Prophet Ascension GW
Enchantment R
At the beginning of each end step, if your life total is greater than your starting life total, you may put a quest counter on Prophet Ascension.
As long as Prophet Ascension has ten or more quest counters on it, your life total cannot be reduced below your starting life total.
IIW: Lands which directly interact with win conditions, two examples would be (1) introducing new win conditions or (2) making it so that certain players can't win or lose.
Planeswalker - Venju M
IIW: Lands with abilities that specifically state "you win the game."