Last 3 Edits
Dec 9th, 2015. Moved to own page.
You are a master of arms and armor that can withstand great punishment. You have been trained extensively in the art of war. You rely on using your weapons and armor to their full extent and outlasting the enemy. Other terms that may suit this archetype include: Defender, Juggernaut, Hearth Guard, Master At Arms. It is also an appropriate archetype to represent knights and cavaliers when combined with the appropriate Background (Noble) and Feats (Inspiring Leader, Mounted Combat).
The following feats are popular with Warmains: Durable, Heavy Armor Master, Resilient, Sentinel, Shield Master, Tough.
When you take this archetype at 3rd level, you gain advantage on all saving throws made to resist the frightened condition. At 10th level, you become immune to the frightened condition.
MIGHTY STRIKE STANCE
Also at 3rd level you can adopt a strong stance and swing hard. When you take the Attack action and hit a target with a melee weapon attack with a weapon that does not have the finesse or light quality, you can add your Constitution modifier to the damage. This stance lasts for 1 minute. It ends early if you are knocked unconscious or move more than 5 feet in a single round (including forced movement). You can use this feature 2 times. This becomes 3 times at 7th level, 4 times at 10th level, 5 times at 15th level and 6 times at 18th level. Once you have no uses left of this feature, you must finish a long rest to use it again.
Also at 3rd level, when you use your shield to make a weapon attack, you do not lose its defensive property. In addition, shields gain the light quality for the purposes of fighting with two weapons, when you wield them.
Warmains typically have armor adjusted for their body and fighting styles. At 7th level, you can doff and don armor in half the time it normally takes (PHB p146) and your armor only contributes half of its weight for encumbrance purposes.
In addition, if your armor is subject to 'damage' or an effect that reduces its AC value (such as due to a critical or a gray ooze attack), you reduce the penalty to your armor by 1. You must complete a short rest before you can use this feature again.
CHINK IN THE ARMOR
At 10th level all of your weapon attacks (except those made with light or finesse weapons) gain the Armor Penetration 1 (AP1) quality. If a weapon already has this quality, increase its AP by 1. (See the En5ider article As Good As His Blade for the armor penetration property).
WEAPON FOCUS GROUP
Also at 10th level, you choose one Weapon Group. Attacks with weapons that do not have the light or finesse qualities from this group, score critical hits on a 19-20 and gain AP1 (which stacks with the above feature).
OFFENCE IS THE BEST DEFENSE
At 15th level, whenever you deal damage to a target with a weapon attack, the creature damaged has Disadvantage on attack rolls made against you until the start of your next turn.
At 18th level, you can shake off all minor wounds. At the start of each of your turns, you regain hit points equal to 5 + your Constitution modifier if you are above half of your maximum hit point total. (CNOTE: This is like the Survivor feature from the PHB, but purposefully changes from below half hit points to above. Hit points above half should be more easily brushed aside).