Here is the full list of all 21 Intralism achievements.
Play 5 maps in relax mode
Complete 10 (different) official maps in normal mode
Up your profile to level 10
Swich workshop filter in maps list from "trend"
Recieve your rank
Create new level in editor
Find authors list
Win multiplayer match
Play multiplayer game with other player
Complete level in multiplayer
Play multiplayer match with workshop level
Play multiplayer game alone
Subscribe to any level in workshop
Find your items
Lose within second after checkpoint and resume from it
Launch Intralism
Collect at least one item of each rarity