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