Loyalty's Proof  

'You put me in a difficult situation, Name. I cannot in good conscience help you without first administering a test of your character, but if you are indeed sent by Aragorn, any delay is an affront to my lord.

'I will not make this decision alone. Render your aid to the rest of my brethren, to Astiul, Forchon, and Naethmunn. Once they are satisfied that you are indeed of good character and do not have villainous motives, I will consider your petition once more.

'You will find my fellow Rangers here at Tinnudir. If, however, you prove false, I will have you cast into the lake with any of your robber-friends that I catch!'

Calenglad has asked you to render your aid to three of his brethren. When they are satisfied that you are true of heart and do not harbour plans to plunder the tombs of the Dunedain, he will consider your errand again.

Objective 1
Earn Astiul's trust
Earn Forchon's trust
Earn Naethmunn's trust
The Rangers Astiul, Forchon, and Naethmunn are at the Ranger-camp on the island of Tinnudir, in Evendim.

Calenglad has asked you to render your aid to three of his brethren. When they are satisfied that you are true of heart and do not harbour plans to plunder the tombs of the Dunedain, he will consider your errand again.

Objective 2
Talk to Calenglad
Calenglad is at the Ranger-camp on the island of Tinnudir, in Evendim.

You have satisfied his brethren of your true heart and should now return to Calenglad to ask him again for aid in acquiring the Silithar for Aragorn

Be sure to complete the quests for each of the three. This is how you gain their trust.