Well, there have not yet been any replies yet, so I thought I would clarify for the sake of clarification. Who knows, maybe someone else will have the same question and thus benefit from the correct answer: the Crystal Crypt does in fact require unlocking through a questline. The line begins with Kay at Ashaya village, who wants you to talk to Andy in the Back Alley about why he refuses to sell her one of his crystal circlets. Kay wants a circlet as a present for her sister Jasmine. When having the conversation with Andy, you will have to say specific things to successfully complete the quest. Mentioning his circlets, asking why he refuses to sell to Kay, and then saying you feel that he is being dishonest are all essentials during the conversation. Note: to call Andy out on being dishonest, you will have to "raise an objection" during which the word "objection" will appear in a spiky bubble in caps locked letters. Andy will ask you what you are doubting him on, and you will have to say the raise in price, and offer to help him afterwards. Andy will turn you away, and Kay will give you another quest after you report to her upon completing the first.
For the second quest, you are to travel to Yvonne, an NPC located at the Broken Bridge. To get there, travel through Frostspike Forest (west of Ashaya Village). You can either walk straight through or cut through Energy Forest by taking the closer portal (if you are like me and hate the ugly faces of frostspike lizards.) Walk up the icicle (branch?) to get to Crystalthicket something (forgot the exact name, sorry) and walk up the hill, taking the lower portal to Emberberry Valley. Walk through the valley and take the east portal to get to the Broken Bridge. Yvonne is to the lower right of the room, with a Distraught Hatchling. Yvonne will give you a quest for a Diamond of Glaciers from a Galepeak chest. Travel to Galepeak Caverns and loot a chest, it should appear on the first one you open (it did for me). Report back to Yvonne and then follow in the lizard's footsteps as you take control of it and lead it through the Exile Camp. Use your lizard's skills to drop the note it has on the Crystal Crate to the lower right of it, right before the tent on the lowest level of exiles.
The lizard's skills are:
1.) Auto Attack (useless, do not use it)
2.) Burrow (allows you to burrow into the snow, becoming undetectable unless you were already seen. Lasts up to a minute, five second cooldown, recast while burrowed to unburrow. Use this move to clear the camp safely.
3.) Throw snowball (throws a snowball at your target, blinding them for 1.5 secs. They will be unable to track your exact movements but will go to the spot they last saw you at, which is where you used the skill. Use this skill and combo with Burrow if an exile noticed you. If you burrow while the exile is blinded, they will not notice you burrow. 30 sec cooldown)
4.) Drop note (drops the note if you are in proximity to the Crystal Crate, actually more a barrel, has a blue crystal on it at the spot above mentioned. Takes around a second to drop the note.)
Also note that you will have to remain undiscovered for fifteen seconds after dropping the note. Do this by burrowing. If you get interrupted while dropping the note, you will not drop it. All the guards move in a specific pattern at intervals, and it is possible to do the quest by yourself, I did it like that. Given how frustrating it is to find the patterns of the exiles, note that this quest can be completed with friends who can distract guards for you. They will have to interact with the Distraught Hatchling by Yvonne and also be in your instance of the room, so you will have to party up. After completing the quests outlined above, an exile will read the note on the crate, and the Crystal Crypt will be open up "for inspection." In reality, it will be open for you to raid. Forever. Hope this makes it more clear how the Crypt gets unlocked :)