A Reddit User posted this deck idea of a Mono-Blue Mill archetype for Standard post-release of GRN. I have known before of this strategy utilizing the Blue and Black colors. A teammate built this deck in Modern but the access to more powerful cards made it very effective in most of its matchups. In the current Standard format, we shall check which card components can be added. We start with the core Blue cards Psychic Corrosion and the new card Drowned Secrets. Here below are some card options categorized to its use.

Creature Threat – Tempest Djinn, Dream Eater, Murmuring Mystic, Homarid Explorer
Board Wipes or Stall – River’s Rebuke, Sleep
Spot Removal – Selective Snare, Blink of an Eye, Deep Freeze
Card Draws or Value – Chemister’s Insight, Mission Briefing, Opt, Radical Idea
Counterspells – Sinister Sabotage, Syncopate, Negate, Disdainful Stroke

Here is the first version of the deck, Mono-Blue Mill:

Creatures
2 Dream Eater
2 Murmuring Mystic

Spells
3 Blink of an Eye
3 Chemister’s Insight
3 Deep Freeze
4 Drowned Secrets
3 Opt
4 Psychic Corrosion
2 Radical Idea
2 Mission Briefing
4 Sinister Sabotage
2 Syncopate
1 Disdainful Stroke
1 Patient Rebuilding

Lands
1 Arch of Orazca
19 Island
4 Memorial to Genius