this dragon is the deadlyest thing iv ever had to fight never again 

1/5 rateing

Lair actions come from being in a lair nothing to do with level or age

You're thinking of legendary actions 

Quote from tigerlevesque >>

@Icemiser Where did you read this. There is no mention of this restriction in the Monster Manual. Legendary actions only apply to adult or older but lair actions seem to apply regardless of age.

 But the stat blocks don’t show Lair Actions for Young Dragons or Wyrmlings, so Lair Actions DO apply only to Adult or older dragons.

Quote from moodlemurphy >>

baby dragon

 Young Dragons are not babies, Wyrmlings are.

Quote from DM_sometimes >>

Would anyone recommend this or a wyvern for a bossfight? For a party of 4 lvl 5 characters? 

 The CR of a Young Black Dragon is 7, which is way too high for a Level 4 or 5 party to face. It really depends on how MANY players you have.

Quote from SeerInc >>

Alone? No. It'll get destroyed. However, no dragons are ever "alone". An encounter that I'm building for 5 7th level characters involves layers and using lair actions.

It's set in the underground basement of a castle (I'm running my modified ToD campaign).

Let me describe the layers first.

Black dragon lairs are inundated with scorpions and snakes and insects. So I'll use a couple of giant scorpions and centipedes as well as a few swarms, both insect and snake.

The young black dragons were recently hatched and are being taught by the Cult. 

There are also several black guard drakes around.

Since black dragons are amphibious, there is a huge, contaminated glacial pond that is fed by the nearby swamp. Generally, this is where the dragons will be found. But, in addition to the dragons, there are also several giant crocodiles.

Yes, it looks way OP for my group, but they can handle it and they need to know that.

This will be the final boss fight on this level.

 How recently did the Dragon hatch?

mood

my players nearly did a tpk. Not because of the dragon. The wild magic sorcerer ate a card (witch is how he dose wild magic) and blew up and killed him self but every one else rolled nat20's and survived. ????????

Quote from SolarLynx >>

Quote from tigerlevesque >>

@Icemiser Where did you read this. There is no mention of this restriction in the Monster Manual. Legendary actions only apply to adult or older but lair actions seem to apply regardless of age.

 But the stat blocks don’t show Lair Actions for Young Dragons or Wyrmlings, so Lair Actions DO apply only to Adult or older dragons.

 Do you not have the digital monster manual?