Arachnogenesis

Create X 1/2 green Spider creature tokens with reach, where X is the number of creatures attacking you. Prevent all combat damage that would be dealt this turn by non-Spider creatures.

Argothian Pixies

Argothian Pixies can't be blocked by artifact creatures.
Prevent all damage that would be dealt to Argothian Pixies by artifact creatures.

Argothian Treefolk

Prevent all damage that would be dealt to Argothian Treefolk by artifact sources.

Angelsong

Prevent all combat damage that would be dealt this turn.
Cycling {2} ({2}, Discard this card: Draw a card.)

Angel of Suffering

Flying
If damage would be dealt to you, prevent that damage and mill twice that many cards.

Alabaster Potion

Choose one —
• Target player gains X life.
• Prevent the next X damage that would be dealt to any target this turn.

Amulet of Kroog

{2}, {T}: Prevent the next 1 damage that would be dealt to any target this turn.

Angel of Salvation

Flash; convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Flying
When Angel of Salvation enters the battlefield, prevent the next 5 damage that would be dealt this turn to any number of targets, divided as you choose.