Origin Feat (Prerequisite: Viking Background)

You gain the following benefits.

Viking Training. You gain proficiency with light armor, medium armor, shields, battleaxes, handaxes, shortswords, longbows, longswords, spears, shortbows, and vehicles (water).

Shield Wall. You can activate this ability as a bonus action, or as a reaction in response to a hostile creature you can see making an attack roll. You attempt to lock shields with one or more friendly creatures that you can see within 5 ft of you. That friendly creature(s) must also have this feat, and they must use their reaction to activate this ability as well. If there are no creatures within 5 ft of you that reciprocate the action, the ability fails. If at least one friendly creature reciprocates the action, you and each creature who's shield (s) are locked with yours gains the benefits of half cover for the duration of the shield wall. When a shield wall is formed, one creature must be designated as it's leader. Every other creature in the formation moves with the shield wall leader, and must forego all movement on their own turn unless they choose to leave the shield wall (no action required). 

In addition, any creature that is behind a shield wall within 10 ft of it also gains the benefit of half cover, or three quarters cover if they are small sized or smaller.