

You can either farm for the last element, or simply leave it for the second playthrough. It is possible to get 2/3 easily while completing the story while be slightly short on the last element. While it technically isn't missable as you can farm exp after the final boss inside the dungeons, this is just to prepare you to do as little work as possible.

There is an achievement for each element to obtain 3 skills in each element. There are three elements in Braveland Wizard: Ice, Nature and Fire.
#BRAVELAND REPUBLI SERIES#
Going to the tower will prompt him to ask you a series of questions that you must answer correctly in order to get the achievement. The final missable achievement is the sage that appears at the crossroad before the final boss behind a golem fight in the desert. Simply use an infernal summon near the mage, then bombard him with both the infernal and the mage. The easiest way to beat this fight (on hard) is to just use the Mage (last unit) as well as picking up the Infernal summon. The achievement requires you to complete that fight while using less than 5 units. After entering the desert, the middle path will have a very difficult fight where you'll be up against whatever characters you pick in your squad except with numbers depending on difficulty and how many men you have hired for that class. The second missable achievement is the mirror fight. If you join the rebellion, the achievement is lost for this playthrough. Refuse to join the rebellion for Law Abiding Citizen. To your right, you will encounter a goblin talking about a rebellion. The forest deity will thaw out the ice and a woody forest will emerge. The first one occurs right after you encounter the forest deity. There are 3 more storyline achievements that are missable depending on your actions. If you do hard only, you will get the no easy one. There's also another achievement that requires you to play without touching easy difficulty. One of the playthroughs will require you to play on the Hard difficulty and you can never move off of this difficulty during the playthrough through the settings nor by prompt should you fail a level too often. Due to the fact you can pick the same ending twice, I would consider this to be missable. In order to finish this game, you'll need two playthroughs to be able to get the Director's Cut Achievement where you must complete both endings which is chosen at the last boss.
