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