The game's collection data lists Glacial Tidestorm as sold by a vendor NPC in Elysian Hold.
Vendor
Zone
Map
Waypoint
Other items it sells
NPC #175523
Elysian Hold
-
-
207
Vendor NPC, zone and position come from the client's collection source tables (CollectableSourceInfo and CollectableSourceVendorSparse); coordinates are the in-game map readout.
Build history
First seen in build 12.0.7.68887 (Midnight (patch 12.0.7)).
Blizzard numbers items as they are created, so the named items next to ID 166705 (166700 to 166714) were usually added in the same batch as Glacial Tidestorm: the same quest line, zone, vendor or reward set.