You may cast Dragon spells without paying their mana costs.

Flash (You may cast this spell any time you could cast an instant.)
When Venser enters, return target spell or permanent to its owner's hand.

Artifacts and creatures entering the battlefield don't cause abilities to trigger.

Reach
Whenever this creature or another Cat you control enters, you may destroy target artifact or enchantment.

(: Add or .)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Flying, vigilance
Whenever a Dragon you control attacks, tap target nonland permanent an opponent controls. That permanent doesn't untap during its controller's next untap step.

(Gain the next level as a sorcery to add its ability.)
When this Class enters, create a 1/1 blue and red Otter creature token with prowess.
: Level 2
When this Class becomes level 2, return target instant or sorcery card from your graveyard to your hand.
: Level 3
Whenever you cast an instant or sorcery spell, create a 1/1 blue and red Otter creature token with prowess.

Cumulative upkeep—Exile the top card of your library. (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.)
When a player doesn't pay this enchantment's cumulative upkeep, that player exiles all cards from their library.
Exile the top card of your library: Prevent the next 1 damage that would be dealt to you this turn.

Activated abilities of artifacts and creatures can't be activated unless they're mana abilities.

You may choose not to untap this creature during your untap step.
As this creature enters, an opponent chooses a creature type.
: Gain control of target creature that isn't of the chosen type for as long as this creature remains tapped.

Lifelink
, : Another target creature you control gains lifelink until end of turn.
Whenever you gain life, put a +1/+1 counter on target creature you control. If you have a full party, put three +1/+1 counters on that creature instead.

Whenever one or more Elves you control attack, they gain deathtouch until end of turn.
Each creature you control has "Whenever a mana ability of this creature resolves, put a number of +1/+1 counters on it equal to the amount of mana this creature produced. This ability triggers only once each turn."

Umbris gets +1/+1 for each card your opponents own in exile.
Whenever Umbris or another Nightmare or Horror you control enters, target opponent exiles cards from the top of their library until they exile a land card.

Add .

Equipped creature gets +1/+1 for each Swamp you control.
Equip—Pay 3 life. (Pay 3 life: Attach to target creature you control. Equip only as a sorcery.)

: Add .
: Add . Activate only if you control a Swamp or a Forest.

Flying
Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
: Skithiryx gains haste until end of turn.
: Regenerate Skithiryx.

Flying
If you would lose the game, instead exile this creature and your life total becomes equal to your starting life total.

Constellation — Whenever Calix or another enchantment you control enters, put a +1/+1 counter on target creature.
Whenever Calix or an enchanted creature you control deals combat damage to a player, you may create a token that's a copy of a nonlegendary enchantment you control. Do this only once each turn.

This spell can't be countered.
: Target spell can't be countered.