Byrdonis Egg is a Quest card in Slay the Spire 2. It starts as an unplayable card in your deck, and it only changes once you bring it to a Rest Site and choose Hatch.
Quick answer: Find the Byrdonis Nest event in a ? room, pick Take the Egg, then go to a Rest Site and select Hatch.
Byrdonis Egg trigger
The trigger is simple and exact. Byrdonis Egg comes from the Byrdonis Nest event, which appears in an Event room marked with a question mark on the map.
That event gives you two choices. One raises your Max HP by 7. The other adds Byrdonis Egg to your deck. If you want to hatch the egg, you must choose Take the Egg.
| Event | Choice | Result |
|---|---|---|
| Byrdonis Nest | Eat the Egg | Gain 7 Max HP |
| Byrdonis Nest | Take the Egg | Add Byrdonis Egg to your deck |
Byrdonis Nest event | Image credit: Mega Crit (via YouTube/@Friendly Frenzy Games)How to hatch Byrdonis Egg
Step 1: Reach a Rest Site after taking Byrdonis Egg. Rest Sites are the campfire rooms on the map.
Step 2: At the Rest Site, choose Hatch. This is the action tied to Byrdonis Egg’s Quest condition.
Step 3: Finish the Rest Site action. Choosing Hatch uses that site’s single action, so you cannot also Rest or Smith there.
How to know Byrdonis Egg worked
The card changes in your deck. Byrdonis Egg is removed and replaced by Byrd Swoop, so the unplayable Quest card is no longer taking up a draw.
If you still see Byrdonis Egg in your deck, the trigger has not been completed. The completed state is the presence of Byrd Swoop instead of the egg.
Byrd Swoop reward
Hatching Byrdonis Egg gives you a colorless attack card called Byrd Swoop. It costs 0 energy and deals 14 damage.
| Card | Cost | Effect |
|---|---|---|
| Byrd Swoop | 0 | Deal 14 damage |
| Byrd Swoop+ | 0 | Deal 18 damage |
Because it is colorless, Byrd Swoop can fit into any character’s deck. The important part for the hatch itself, though, is that the reward fully replaces the Quest card rather than sitting beside it.
What stops the hatch
There are only a few hard blockers.
| Problem | What it means |
|---|---|
| You chose Eat the Egg | You never added Byrdonis Egg to the deck, so there is nothing to hatch |
| You have not reached a Rest Site | The Quest condition has not been met yet |
| You used Rest or Smith instead | You spent the Rest Site action on something else and must wait for another site |
The whole sequence is short once you know the trigger. Take Byrdonis Egg from Byrdonis Nest, reach a Rest Site, choose Hatch, and confirm the result by checking that Byrdonis Egg has turned into Byrd Swoop.