Here is the full list of all 49 A Druid's Duel achievements.
Use 3 Eagles to attack in one turn.
Transform a Wind Rider into an Eagle.
Transform a Guardian into a Wolf.
Destroyed 3 obstacles in one turn.
Create 3 obstacles in one turn.
Generate 20,000 lifetime Mana in Campaign and Online play.
Spawn 100 new units.
Transform a Snarlclaw into a Bear.
Transform a Waywalker into a Turtle.
Use 3 wolves in one turn.
Change the same Wind Rider into an Eagle twice in one turn.
Kill a Turtle with a Bear.
Capture 2 Relics in one turn.
Capture 4 Relics in one turn.
Build 4 Bridges in one turn.
Build 2 Bridges in one turn.
Destroy a piece of land with an Obstacle on it.
Generate 120 Mana in one turn.
Attack 3 times in a row with one Bear.
Start a new Online Game.
Start 5 new Online Games.
Finish an Online Game.
Finish 5 Online Games.
Take 1st place in an Online Game.
Win 3 Online Games.
Win 10 Online Games.
Win 20 Online Games.
Take 2nd in an Online Game.
Take 3rd in an Online Game.
Take 4th in an Online Game.
Rise to Wolf Rank in Online play.
Login to Online Play 10 times.
Rise to Eagle Rank in Online play.
Rise to Bear Rank in Online play.
Rise to Turtle Rank in Online play.
Earn 50 Aura in a single Online Game.
Earn 10 Trisks in a single Online Game.
Earn 20 Trisks in a single Online Game.
Earn 250 Trisks in Online Play.
Defeat Master Rickett.
Defeat Master Ninonell
Win 1 Map Item.
Win 4 Map Items.
Win the Highsommar Season Stone.
Win the Aldenfalle Season Stone.
Win the Wintermourne Season Stone.
Win the Deepwinter Season Stone.
Win the Beltaine Season Stone.
Win the Midsommar Season Stone (and the game!)