Here is the full list of all 31 Idle Clans achievements.
Create a clan
Smith a piece of Astronomical armour
Reach max level in a skill
Steal from the royal clan
Join a minigame
Purchase the most glamorous property available
The true test for any respectable chef... Make a pizza.
Defeat a boss
Reach level 100 in a skill
Grow some watermelons
Create a godlike item
Defeat a dragon
Battle a monster with an Outstanding weapon
Perform a leaderboard search
Receive a boss key
Achieved upon reaching your first million
Purchase your first property. It's nothing to brag to your parents about, but it's a start.
Enchant an item
Send an item to your clan's vault
Equip diamond jewellery
Eat a burger in battle
Prepare a special dish
Create silver jewellery
Refine an item
Join a clan
Purchase an upgrade
List an item for sale
Plunder a small, helpless village
Your first level up
Complete the tutorial
Reach a billion gold