The Elden Ring: Shadow of the Erdtree's Hornsent Grandam quest, or "Horny Grandma" as we (I) have dubbed her at PCG, is definitely a minor character in Elden Ring's beastly expansion pack, but she has a surprising number of interactions available throughout the expansion, and they are somewhat hidden.
Below I've outlined how to find the Hornsent Grandam in the first place, how to first unlock her dialogue and special soup, and when to come back and talk to her again later in your journey through Elden Ring: Shadow of the Erdtree.
You can find the Hornsent Grandam in Elden Ring: Shadow of the Erdtree's first legacy dungeon, Belurat Tower Settlement. After the Private Altar site of grace, which is the second you'll encounter proceeding through the dungeon, the Hornsent Grandam is in the room across the bridge with the sniper enemies who fired at you on the way to the Private Altar.
To unlock the door, you'll need the Storeroom Key, which is located further into Belurat's upper area after the Private Altar. You'll want to head west from the grace, either killing or avoiding the difficult Hornsent Knight enemy just outside the Private Altar Room. You'll have to turn north to curve around the nasty yellow waterfall. When you're in the stream leading to that waterfall, look for a door opening into a wood paneled room with a ladder in the middle.
On the second floor, you'll find the Storeroom Key just before the door. Stick around this area to also find the Well Depths Key and open the other locked door in the first half of Belurat.
The Hornsent Grandam will have some choice words about Marika and the Golden Order when you first talk to her, but to unlock more, you'll have to beat the Divine Beast Dancing Lion boss of Belurat, Tower Settlement and steal his nifty headgear, that oversized lion head you just know all the rudest PvP boys are going to start wearing.
Talk to the Hornsent Grandma again while wearing the Lion mask and she'll tell you more about Hornsent society, as well as giving you the Watchful Spirit spell. Leave and return once more (you don't have to wear the lion mask anymore) for more dialogue and Scorpion Stew, a nifty but inessential healing consumable.
You can come back for more stew after eating what she gave you, but the next big change (and the conclusion of her quest) comes once you beat Messmer the Impaler. Talk to her yet again for more lore and Gourmet Scorpion Stew, a slightly improved but still inessential healing consumable.
If you return later, she'll have no more dialogue, but you can pick up another Gourmet Scorpion Stew. Yum. And you didn't hear it from me, but maybe also check in with her one more time once you've beaten the DLC's final boss.
