This is obtained after completing the Soul Survivor quest and requires you to first talk with Gribbly the Gallant in the Sanctum's Prison room.

The Keys To Trust is very simple and is mearly a quest to move you onto the next portion of the Qeynos Claymore Quest line. Upon reaching the Sanctum of the Scaleborn Prison room you will see a froglok in the prison called Gribbly the Gallant. If you have completed the Soul Survivor quest he will give you this quest. He will ask you to kill the named jailor that spawns in the prison room. Unfortunately this becomes a camping mission where you may need to kill the PH or common jailor up to nine times to get the named jailor to spawn.

After you have managed to spawn Restrainer Drovbaazz and kill him successfully you will get an update for your quest. After obtaining the keys you will be instructed to take them to the named froglok in the Hidden Refuge in the Tenebrous Tangle zone. The named froglok is Lady Erollisi and upon giving her the keys you will be pointed to another NPC down further in the Sanctum of The Scaleborn named Amygdalan Xhorroz. Xhorroz is a hard NPC to reach and is quite a ways down into the Sanctum in an area called the Invoker Pool room.

Amygdalan Xhorroz will continue your quest line with the new quest An Uneasy Alliance.