No missable achievements (plus 30 unknown)
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Escaped the cell in the keep.
Met Rider and he joined your party.
Beat the water monster at the end of the cave.
Traded for the badge.
Met Rios and he joined your party.
Met Gunnar and he joined your party.
Traded for the ring.
Defeated the Witch on the mountain.
Beat the Golems attacking Flowey.
Traded for the key.
Traded for the medallion.
Defeated the invaders on the beach.
Blasted a path through the trench to reach the fortress.
Pleased the farmer to get milk.
Used the medallion to get the looking scope.
Drained the pool in the fortress.
Beat Evil Tiggy in battle.
Freed the prisoner in the keep.
Killed the goblin horde with bow and arrow.
Recovered the staff at the top of the keep.
Travelled to another world.
Found and killed the possessed tree in the jungle.
Killed the Dragon Witch at the top of the volcano.
Met Tipper and he joined your party.
Found a treasure in the forest.
Got the staff from King Albert.
Destroyed the evil staff.
Traded for the light orb.
Watched the end-game credits.
Beat the final boss.