Force skills
Force This is your main mastery tree, because it contains all your healing skills. You want to keep this as high as possible and a good thing about it, is that you can also help those who are higher level than you. So you don't need to be at the top of your guild.
Self heal series This skill is used to heal your own HP. But the heal series do the job much better and can be used on both others and yourself. So no need to waste any SP on this.
Force cure series Works just like an universal pill and heals any curable abnormal status. It is slow compared to the pills but usefull if any of your friends runs out of them. If you feel you got the SP, you can upgrade it just in case.
Heal series Heals alot more HP than self heal series and as told above, you can use it on both yourself and others. Good for a quick HP raise and to give a friend the upper hand in a PvP fight.
Rebirth art series Undoubtedly the most important skill as a healer. Its use is to revive other players and while doing jobs, it will give you a great advantage when facing an enemy. You can heal players up to ten levels above you, assuming you have the the Force mastery at the same level as yourself.
Natural therapy series A really helpfull skill, both for jobs and when killing mobs. It brings out a large ring, when inside you are safe from mobs up to a certain level. It also provides a faster HP and MP regrowing rate while resting. You are not safe though from champion-, elite-, giant- or unique mobs who can attack you inside of it. If a trade animal goes down, put this up around the trade goods. To be able to bring out a new one, you must stay away from being atacked within 20 seconds. Having this as a protection makes it all much easier.
Vital spot attack series You get two skills out of this, vital spot-muscle and vital spot-spirit. The first one is used to decrease someone's parry ratio and the second one to decrease someone's attack rating. It lasts for ten seconds when inflicted and has a good regrow rate so you can hit many targets fast. The vital spot-muscle can be really usefull on STR builds because of their large amount of HP. When the parry ratio is lowered, the target will recive more damage. And for nukers or other hard hitting builds, a decreased attack rating will make their attacks weaker. You can inflict your target with both of them at the same time and the status can not be cured with uni pills. These skills can be used at any time without getting offender status. Its even possible to use them in a city's safe zone.
Force increasing series This skill is a passive one and adds up on your MP. Very usefull because you will have a low amount of MP due to your STR build.
Lightning This mastery is what gives the build a good survival rate. You need to be able to avoid being targeted by several enemys and the best skill for that is imo speed. The lightning tree also provides increased parry ratio so you recieve lower damage.
Thunder force series This will be your weapon imbue. Just like fire and ice, it adds up some extra power to your weapon. It has a transfer rate of 3m and give away extra damage to two nearby targets, so be prepared to agro mobs around you when fighting. Not much of a problem though, as you have plenty of HP to your advantage compared to an INT build. It will also inflict your target with electricity, which lower the parry ratio. For mobs this is usefull, while player enemys can easily cure the effect with uni pills.
Piercing force series It increases the magical damage (INT build) you deal with a certain percantage. Not much of use, because you deal mostly physical damage (STR build).
Wind walk series This provides two skills. Grass walk, which will increase your moving speed and ghost walk-phantom, which teleports you a few meters away at the direction of your mouse pointer. These two skills are the main reason of choosing lightning and not ice or fire. You will be hard to team up on and maybe even imposssible to catch, if your enemy has lower level of grasswalk.
Lion shout series No use to you because it is a magical damage attack. The weapon masterys have got better ranged skills for your build.
Concentration series This skill temporarily increas your parry ratio and will lower the damage you take. A good defensive skill that you need.
Thunderbolt force series Same as Lion shout series, a ranged magical attack that is not very useful to your build.
Heaven's force series This skill is a passive one and also adds up on your parry ratio like concentration series. So you should get this one too.
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Hope this guide will inspire you to choose the force mastery as one of your main skills. Going lightning as a blader may sound weird because it is not very common. But it is the speed you are after in this build, and not the highest dealing damage like fire or the longest survival rate like ice. You will in some situations stay away from fighting and only act as support. No need to be a super tank (someone who can withstand a lot of damage) like ice bladers or higher damage dealer like fire bladers.
Having three main mastery trees may sound alot. But I haven't notice any hard time getting enough SP for them. I even leveled up all the force skills and my weapon skill up to 32 before I decided to go with lightning and force together with bicheon.
This is not said to be the best healer build. Everthing is based on my own thoughts of which skills that may help you out the most. The more different builds there are, the more usefull they all get. So get inspired, have some thinking done and then choose the way you feel is the best to go.