Here is the full list of all 167 RPG MO achievements.
Discover Dungeon I map
Discover Whiland map
Play for a year
Reach 30 forging
Reach 30 mining
Reach 30 fishing
Reach 30 cooking
Reach 30 accuracy
Reach 30 strength
Reach 30 defense
Reach 30 health
Finish Tutorial Island
Reach 30 magic
Reach 30 alchemy
Reach 30 woodcutting
Reach 30 farming
Reach 30 jewelry
Reach 30 carpentry
Reach 30 breeding
Reach 60 accuracy
Reach 60 strength
Reach 60 defense
Reach 60 health
Reach 60 magic
Reach 60 alchemy
Reach 60 woodcutting
Reach 60 farming
Reach 60 fishing
Reach 60 cooking
Reach 60 jewelry
Reach 60 carpentry
Reach 60 forging
Reach 60 mining
Reach 60 breeding
Reach 90 accuracy
Reach 90 strength
Reach 90 defense
Reach 90 health
Reach 90 magic
Reach 90 alchemy
Reach 90 woodcutting
Reach 90 farming
Reach 90 fishing
Reach 90 cooking
Reach 90 jewelry
Reach 90 carpentry
Reach 90 forging
Reach 90 mining
Reach 90 breeding
Unlock normal party quest difficulty
Unlock hell party quest difficulty
Log in every day for 100 days
Successfully craft a piglet
Acquire or buy 1000 MOS
Unlock 2nd chest page
Unlock 3rd chest page
Unlock 4th chest page
Unlock 5th chest page
Reach to the end of Cathedral
Reach to Cathedral level 50
Open a Rare Present
Become a premium member
Kill an Acid Dragon Lord
Kill an Ancient Hydra
Kill a Pharaoh
Kill a Nephilim Warrior
Kill a World Tree
Kill a Diablo
Reach 30 fletching
Reach 30 archery
Reach 60 fletching
Reach 60 archery
Reach 90 fletching
Reach 90 archery
Kill a Titan Minotaur
Kill a Blood Eagle
Unlock hard party quest difficulty
Reach 30 wizardry
Reach 60 wizardry
Reach 90 wizardry
Kill a Cave Crawler
Kill a Giant Cyclops
Kill a Demon Overlord
Kill an Orc Overlord
Kill a Venus Flytrap
Kill a Reaper
Kill a Demon Portal
Kill a Chaotic Dragon
Kill a Raguel The Archangel
Kill a Cannibal Plant
Kill a Giant Tarantula
Discover Reval map
Discover Pernau map
Discover Ancient Dungeon map
Discover Clouds map
Discover No Man's Land map
Discover Lost Woods map
Discover Rakblood map
Discover Narwa map
Discover Fellin Island map
Discover Dragon's Lair map
Discover Hell map
Discover Moche II map
Discover Dungeon IV map
Discover Wittenstein map
Discover Cathedral
Discover Void I map
Discover Nature Tower
Discover Ice Tower
Discover Fire Tower
Discover Blood River map
Discover Star of Knowledge map
Discover Witches I map
Discover Core of Knowledge map
Discover Walco map
Discover Devil's Triangle map
Discover Broceliande Forest map
Reach 120 accuracy
Reach 120 strength
Reach 120 defense
Reach 120 health
Reach 120 magic
Reach 120 wizardry
Reach 120 alchemy
Reach 120 woodcutting
Reach 120 farming
Reach 120 fishing
Reach 120 cooking
Reach 120 jewelry
Reach 120 carpentry
Reach 120 forging
Reach 120 mining
Reach 120 breeding
Reach 120 fletching
Reach 120 archery
Unlock 6th chest page
Discover No Man's Dungeon map
Discover Tavern map
Discover Lost Relic map
Discover Heaven map
Discover Purgatory map
Visit your island
Visit your dungeon
Reach 30 fungiculture
Reach 60 fungiculture
Reach 90 fungiculture
Reach 120 fungiculture
Reach 3% skilling bonus
Add 10 items to the Collection Book
Add 50 items to the Collection Book
Add 150 items to the Collection Book
Add 250 items to the Collection Book
Add 350 items to the Collection Book
Add 450 items to the Collection Book
Add 550 items to the Collection Book
Add 650 items to the Collection Book
Visit your premium map
Add every seed to the decorative soil
Add every spore to the decorative sawdust plot
Complete 5 quests
Complete 20 quests
Complete 35 quests
Complete 50 quests
Add 750 items to the Collection Book
Add 850 items to the Collection Book
Add 950 items to the Collection Book
Unlock an extra drop