Gravity Sphere causes all creatures to lose flying.
Moat prevents non-flying creatures from attacking, and since no creatures can have flying, no creatures can attack.

Creatures can't attack

Lock

Gravity Sphere

Moat

Gravity Sphere causes all creatures to lose flying.
Form of the Dragon prevents non-flying creatures from attacking you, and since no creatures can have flying, no creatures can attack you.

You can't be attacked

Form of the Dragon

At the beginning of your draw step, Island Sanctuary causes you to skip your card draw, and prevents creatures without flying and/or islandwalk from attacking you.
Because Gravity Sphere causes all creatures to lose flying, only creatures with islandwalk can attack you.

Most creatures can't attack you

You do not draw cards during your draw steps

Island Sanctuary

Gravity Sphere causes all creatures to lose flying.
Magus of the Moat prevents non-flying creatures from attacking, and since no creatures can have flying, no creatures can attack.

Magus of the Moat

Gravity Sphere causes all creatures to lose flying.
Stormtide Leviathan prevents creatures from attacking unless they have flying and/or islandwalk. Since no creatures will have flying, only creatures with islandwalk can attack.

Creatures without islandwalk cannot attack

Stormtide Leviathan

Sacrifice Felidar Guardian to Altar of Dementia to mill target player for 1.
Luminous Broodmoth triggers, returning Felidar Guardian to the battlefield with a flying counter on it.
Felidar Guardian's ETB triggers, exiling Mystic Decree and then returning it to the battlefield.
Repeat.

Infinite death triggers

Infinite creature ETB

Infinite creature LTB

Infinite mill

Infinite creature sacrifice triggers

Luminous Broodmoth

Felidar Guardian

Altar of Dementia

Sacrifice Felidar Guardian to Ashnod's Altar to add {C}{C}.
Luminous Broodmoth triggers, returning Felidar Guardian to the battlefield with a flying counter on it.
Felidar Guardian's ETB triggers, exiling Mystic Decree and then returning it to the battlefield.
Repeat.

Infinite colorless mana

Ashnod's Altar

Sacrifice Felidar Guardian to Phyrexian Altar to add 1 mana of any color.
Luminous Broodmoth triggers, returning Felidar Guardian to the battlefield with a flying counter on it.
Felidar Guardian's ETB triggers, exiling Mystic Decree and then returning it to the battlefield.
Repeat.

Combos with "Gravity Sphere"