Oaths are certain handicaps chosen by the players before each match that reward you with bonus percentage of experience and gold.
Serpent - health pickups are less effective. (+10% exp, +15% gold bonus)
Sword - ammo pickups are less effective. (+8% exp, +10% gold bonus)
Hound - the player takes more damage (+20% exp, +25% gold bonus)
Spider - the player deals less damage (+20% exp, +25% gold bonus)
Thief - the player has no armor (+30% exp, +30% gold bonus)
Warrior - permanent ability cooldown (+20% exp, +20% gold)
Scorpion - enemy attacks cause poison damage (+25% exp, +25% gold bonus)
-The Warrior oath is considered to be the least handicaping, while giving a considerable experience and gold bonus.
-Always check your enabled oaths before starting a match. Doing so can save you needless frustration and waste of available lives.