Elder Land Wurm

Defender, trample
When Elder Land Wurm blocks, it loses defender.

Chromium

Flying
Rampage 2 (Whenever this creature becomes blocked, it gets +2/+2 until end of turn for each creature blocking it beyond the first.)
At the beginning of your upkeep, sacrifice Chromium unless you pay {W}{U}{B}.

Canopy Dragon

Trample
{1}{G}: Canopy Dragon gains flying and loses trample until end of turn.

Cloud Dragon

Flying
Cloud Dragon can block only creatures with flying.

Viashivan Dragon

Flying
{R}: Viashivan Dragon gets +1/+0 until end of turn.
{G}: Viashivan Dragon gets +0/+1 until end of turn.

Pearl Dragon

Flying
{1}{W}: Pearl Dragon gets +0/+1 until end of turn.

Dragon Whelp

Flying
{R}: Dragon Whelp gets +1/+0 until end of turn. If this ability has been activated four or more times this turn, sacrifice Dragon Whelp at the beginning of the next end step.

Teeka's Dragon

Flying; trample; rampage 4 (Whenever this creature becomes blocked, it gets +4/+4 until end of turn for each creature blocking it beyond the first.)

Mist Dragon

{0}: Mist Dragon gains flying. (This effect lasts indefinitely.)
{0}: Mist Dragon loses flying. (This effect lasts indefinitely.)
{3}{U}{U}: Mist Dragon phases out. (While it's phased out, it's treated as though it doesn't exist. It phases in before you untap during your next untap step.)

Arcades Sabboth

Flying
At the beginning of your upkeep, sacrifice Arcades Sabboth unless you pay {G}{W}{U}.
Each untapped creature you control gets +0/+2 as long as it's not attacking.
{W}: Arcades Sabboth gets +0/+1 until end of turn.

Catacomb Dragon

Flying
Whenever Catacomb Dragon becomes blocked by a nonartifact, non-Dragon creature, that creature gets -X/-0 until end of turn, where X is half the creature's power, rounded down.

Crimson Hellkite

Flying
{X}, {T}: Crimson Hellkite deals X damage to target creature. Spend only red mana on X.

Shivan Dragon

Flying
{R}: This creature gets +1/+0 until end of turn.

Nicol Bolas

Flying
At the beginning of your upkeep, sacrifice Nicol Bolas unless you pay {U}{B}{R}.
Whenever Nicol Bolas deals damage to an opponent, that player discards their hand.

Nalathni Dragon

Flying; banding (Any creatures with banding, and up to one without, can attack in a band. Bands are blocked as a group. If any creatures with banding you control are blocking or being blocked by a creature, you divide that creature's combat damage, not its controller, among any of the creatures it's being blocked by or is blocking.)
{R}: Nalathni Dragon gets +1/+0 until end of turn. If this ability has been activated four or more times this turn, sacrifice Nalathni Dragon at the beginning of the next end step.

Ebon Dragon

Flying
When Ebon Dragon enters, you may have target opponent discard a card.

Firestorm Hellkite

Flying, trample
Cumulative upkeep {U}{R} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)

Fire Dragon

Flying
When Fire Dragon enters, it deals damage to target creature equal to the number of Mountains you control.

Vaevictis Asmadi

Flying
At the beginning of your upkeep, sacrifice Vaevictis Asmadi unless you pay {B}{R}{G}.
{B}: Vaevictis Asmadi gets +1/+0 until end of turn.
{R}: Vaevictis Asmadi gets +1/+0 until end of turn.
{G}: Vaevictis Asmadi gets +1/+0 until end of turn.

Volcanic Dragon

Alabaster Dragon

Flying
When Alabaster Dragon dies, shuffle it into its owner's library.

Palladia-Mors

Flying, trample
At the beginning of your upkeep, sacrifice Palladia-Mors unless you pay {R}{G}{W}.