Ultimate Green Goblin

At the beginning of your upkeep, discard a card, then create a Treasure token.
Mayhem {2}{B/R} (You may cast this card from your graveyard for {2}{B/R} if you discarded it this turn. Timing rules still apply.)

Marauding Mako

Whenever you discard one or more cards, put that many +1/+1 counters on this creature.
Cycling {2} ({2}, Discard this card: Draw a card.)

Hobgoblin, Mantled Marauder

Flying, haste
Whenever you discard a card, Hobgoblin gets +2/+0 until end of turn.

Monument to Endurance

Whenever you discard a card, choose one that hasn't been chosen this turn —
• Draw a card.
• Create a Treasure token.
• Each opponent loses 3 life.

Bloodghast

This creature can't block.
This creature has haste as long as an opponent has 10 or less life.
Landfall — Whenever a land you control enters, you may return this card from your graveyard to the battlefield.

Demand Answers

As an additional cost to cast this spell, sacrifice an artifact or discard a card.
Draw two cards.

Swamp

Iron-Shield Elf

Discard a card: This creature gains indestructible until end of turn. Tap it. (Damage and effects that say "destroy" don't destroy it. If its toughness is 0 or less, it still dies.)

Mountain

Bringer of the Last Gift

Flying
When this creature enters, if you cast it, each player sacrifices all other creatures they control. Then each player returns all creature cards from their graveyard that weren't put there this way to the battlefield.

Inti, Seneschal of the Sun

Whenever you attack, you may discard a card. When you do, put a +1/+1 counter on target attacking creature. It gains trample until end of turn.
Whenever you discard one or more cards, exile the top card of your library. You may play that card until your next end step.

Moonshadow

Menace
This creature enters with six -1/-1 counters on it.
Whenever one or more permanent cards are put into your graveyard from anywhere while this creature has a -1/-1 counter on it, remove a -1/-1 counter from this creature.