Blue Dragon Wyrmling

A blue dragon wyrmling on the party's side is rare, but it's a clean setup if a sorcerer with draconic ancestry hatched it from a stolen egg, or if the party rescued it from kobold captivity and the imprint stuck. The wyrmling thinks of one PC as parent and treats the others as siblings it tolerates, which means it will fight for them and steal their shiny things in roughly equal measure. It is Lawful Evil and twelve weeks old. It has opinions and they are mostly wrong.

In combat, the wyrmling wants to feel important. Lightning Breath is its showpiece: line it up with an enemy cluster, ask the player who imprinted it to give the cue, and let it do 6d6 lightning at DC 12. After the breath, it dives for Rend attacks and does what feels heroic rather than what's tactically sound. If a PC tells it to retreat, it sulks at altitude. If no one tells it anything, it picks the shiniest enemy and bites that one.

The roleplay weight matters more than the damage. A party with a young dragon attached to them is a party with a moral question. Adventurers are going to want the dragon to grow up good, and the dragon is going to want gold, blood, and respect. Have an NPC offer to buy it. Have a metallic dragon notice and disapprove. Make the party justify the relationship to skeptics, because the relationship is the real plot, not the +21 lightning damage.

Ask the player who imprinted the wyrmling to name it in session one, and write that name down. Every time the dragon does something monstrous, use the name in narration. The dissonance carries the arc.

A blue dragon wyrmling is the dragon you put in front of a tier-1 party that needs to feel like they fought a dragon. CR 3, 65 HP, AC 17, and a Lightning Breath that can two-shot a wizard if the dice are kind. The wyrmling is also smart enough (Int 12, Cha 15) to talk, brag, and threaten, which is half the fun. It is a child with a flamethrower attitude and immunity to lightning damage, and it has been told its whole short life that it is the most important creature in the desert.

Open with Lightning Breath if it's available. 6d6 lightning, DC 12 Dex, 30-foot line that's only 5 feet wide. The narrow line is the lever: position the wyrmling so two PCs are stacked along the line. Average 21 damage on a fail will drop a level-3 squishy or chunk a fighter. Recharge 5-6 means you'll likely have it again in a round or two, so it's worth darting out of melee to set up a clean line. After the breath, switch to Multiattack: two Rends at +5, average 11 each (8 slashing plus 3 lightning).

Mobility is the wyrmling's edge. 60 ft. fly, 30 ft. walk, 15 ft. burrow. Don't sit in melee with the fighter. Open the round at altitude, dive for two Rends if the line isn't clean, then climb back out of reach. The party's archers will need to dedicate a turn to bringing it down, and a dedicated turn from the rogue is a turn the rogue isn't sneak-attacking the cult leader you've also put in this scene. Pair the wyrmling with a few cultist minions and the encounter runs itself.

Wyrmlings are arrogant and brittle. Below half HP, this one is suddenly remembering it has a parent who would be furious about its death, and it tries to flee straight up. The party should hear the scream-shriek of a child reptile as it climbs out of bow range. If they let it go, it tells the adult dragon. If they kill it, the adult dragon finds out anyway. Either way, you have a sequel hook.