• Edit:
  I played a bit again and am unsure if it could be solved just by having:
  Synthesis - When you get an Astral flower, you have 50% of getting a shrine.
  
  When you play with higher corruption, you might get multiple astral flowers from the same monster, therefore you get several shrines at once. Now there are multiple monsters. 5 Monster * 10 Astral flowers = 50 Shrines / 50 Buffs.

You do not have to make this mission with 77 Malice, 25 Oblivion or 1000 Corruption.

You only have to own 50 Buffs

As book I choose Jeanne with her second path Revel in Danger, because for every spawned demon she is granted their buffs: "Buffs on demons also apply to you, wherever you are. Chance to Duplicate Elite Buffs +50%"

Important Upgrades:

• Cascade - "Shrine Summoners can appear."
  
• Buff Duration - "+5% Buff Duration (per point)"
  
• Shrine Size - "+5% Shrine Size"

Important Unbindings:

• Unbound Shrine Maiden - "Aura Effect: Buff Duration +20%. Summon a Shrine."
  
• Unbound Synthesis - "Aura Effect: Shrine Summon Rate +13%, Flowers Gained +7%."
  
• Unbound String of Ears - "Aura Effect: Gain 2 permanent copies of a random Shrine buff other than Experience Gain."

I don't know if they are necesary. I had quite an amount of flowers so I leveled them all up to 100.
If it won't work for you with lower leveled demons, you might wanna level them up to.

My Demons for this Achievment:

• Imp - duplicate shrine buffs
  
• Crusher - shrine size
  
• Maggot - duplicate elte buffs, shrine of shrines
  
• Brain Mole - xp, shrine kill requirement
  
• Golem - buff duration
  
• Void Wing - duplicate regular shrines
  
• Void Walker - shrine summon rate

Those I used because they have all something to do with shrines or buffs.

normal Auras:

• Shrine Maiden --> +20% Buff Duration * 12 Upgrades = +240% Buff Duration
  
• Synthesis --> +13% Shrine Summon Rate * 12 Upgrades = +156% Shrines Summon Rate

illegal Auras:

• Heads will Roll --> +30% Buff Duration

arcane Auras:

• String of Ears --> +2 permanent Shrine buffs * 6 Upgrades = 14 permanent Shrine buffs
  
• Grim Row --> +1 Elite Demon when an Elite Demon spawns * 4 Upgrades = 5-7 EliteDemon

normal Weapon:

• Domination / Apex Predator --> When a Elite-Demon dies it spawns it and grant buffs.

Illegal Weapon (interesting, not required):

• Shrinkage --> "[..] Fire a [..] orb that Freezes Demons, and reduces their size and damage."

The remaining Slots were filled by me with weapons that freeze Demons.