Each mark requires its own test.
The Mark of Duty is reserved for those who pass the Trial of Duty. You must be above level 35 to qualify. To take this test visit Grand Master Hannavalt of the Town of Giran.
The Mark of Life is reserved for those who pass the Testimony of Life. You must be above level 37 to qualify. To take this test visit Master Cardien of the Town of Dion.
And last, the Mark of the Healer is only given to those who pass the Test of the Healer. You must be above level 39 to qualify. To take this test visit Priest Bandellos at the Temple of the Town of Giran.