The Viking's stats in Kal Online are the biggest influence on the viability of the class in the long run.
At the higher levels, his extemely poor Magic Defense ends up making him quite vulnerable to magic attacks. There are multiple class C mercenaries with powerful magic attacks which can hit any unit in the opposing formation in the late game of Atlantica Online, and once those mercenaries arrive on the scene, the Viking's lifespan tends to shorten significantly on the battlefield.
Some of the Viking's strengths are his high Strength stat, allowing for high-damage attacks, and his reasonably high Defense and Vitality. These stats allow the Viking to tank pretty decently in the first 40 or so levels of advancement(kalonline geons), but by the mid-game there are several other mercenaries with much better stats for front-line positioning in your formation.
In terms of armor and accessories, It is recommendable to give the Viking equipment which increases his strength and his ability to stay in the fight for as long as possible. Items which increase Strength, Vitality, Defense, and Magic Defense are indispensible for this.
The Viking's real power in most fights is his skill Freezing Axe. Because of the power of this skill, your opponent will probably choose the Viking as one of the first targets to take down, particularly in PvP. So it is a good idea to use equipment which boosts his defensive stats, to increase his survivability.
