Scourge of Valkas

Flying
Whenever Scourge of Valkas or another Dragon you control enters, it deals X damage to any target, where X is the number of Dragons you control.
{R}: Scourge of Valkas gets +1/+0 until end of turn.

Thunder Dragon

Flying
When Thunder Dragon enters, it deals 3 damage to each creature without flying.

Red Dragon

Flying
Fire Breath — When Red Dragon enters, it deals 4 damage to each opponent.

Scourge of the Throne

Flying
Dethrone (Whenever this creature attacks the player with the most life or tied for most life, put a +1/+1 counter on it.)
Whenever Scourge of the Throne attacks for the first time each turn, if it's attacking the player with the most life or tied for most life, untap all attacking creatures. After this phase, there is an additional combat phase.

Ancient Copper Dragon

Flying
Whenever Ancient Copper Dragon deals combat damage to a player, roll a d20. You create a number of Treasure tokens equal to the result.

Torbran, Thane of Red Fell

If a red source you control would deal damage to an opponent or a permanent an opponent controls, it deals that much damage plus 2 instead.

Mountain

Dragon Mage

Flying
Whenever this creature deals combat damage to a player, each player discards their hand, then draws seven cards.

Lathliss, Dragon Queen

Flying
Whenever another nontoken Dragon you control enters, create a 5/5 red Dragon creature token with flying.
{1}{R}: Dragons you control get +1/+0 until end of turn.

Siege Dragon

Flying
When Siege Dragon enters, destroy all Walls your opponents control.
Whenever Siege Dragon attacks, if defending player controls no Walls, it deals 2 damage to each creature without flying that player controls.

Dragon's Approach

Dragon's Approach deals 3 damage to each opponent. You may exile Dragon's Approach and four cards named Dragon's Approach from your graveyard. If you do, search your library for a Dragon creature card, put it onto the battlefield, then shuffle.
A deck can have any number of cards named Dragon's Approach.