Metrognome

When a spell or ability an opponent controls causes you to discard Metrognome, create four 1/1 colorless Gnome artifact creature tokens.
{4}, {T}: Create a 1/1 colorless Gnome artifact creature token.

Spiritual Focus

Whenever a spell or ability an opponent controls causes you to discard a card, you gain 2 life and you may draw a card.

Library of Leng

You have no maximum hand size.
If an effect causes you to discard a card, discard it, but you may put it on top of your library instead of into your graveyard.

Curse of Obsession

Enchant player
At the beginning of enchanted player's draw step, that player draws two additional cards.
At the beginning of enchanted player's end step, that player discards their hand.

Nephalia Academy

If a spell or ability an opponent controls causes you to discard a card, you may reveal that card and put it on top of your library instead of putting it anywhere else.
{T}: Add {C}.

Ajani's Last Stand

Whenever a creature or planeswalker you control dies, you may sacrifice Ajani's Last Stand. If you do, create a 4/4 white Avatar creature token with flying.
When a spell or ability an opponent controls causes you to discard this card, if you control a Plains, create a 4/4 white Avatar creature token with flying.

Anvil of Bogardan

Players have no maximum hand size.
At the beginning of each player's draw step, that player draws an additional card, then discards a card.

Zedruu the Greathearted

At the beginning of your upkeep, you gain X life and draw X cards, where X is the number of permanents you own that your opponents control.
{U}{R}{W}: Target opponent gains control of target permanent you control.

Guerrilla Tactics

Guerrilla Tactics deals 2 damage to any target.
When a spell or ability an opponent controls causes you to discard Guerrilla Tactics, Guerrilla Tactics deals 4 damage to any target.

Psychic Purge

Psychic Purge deals 1 damage to any target.
When a spell or ability an opponent controls causes you to discard Psychic Purge, that player loses 5 life.