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 take the test. To take this test visit Grand Master Hannavalt of the Town of Giran.
The Mark of Trust is reserved for those who pass the Testimony of Trust. You must be above level 37 to qualify. To take this test visit High Priest Hollint at the Town of Oren.
And last, the Mark of the Healer is reserved for 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.