How do I get Torom to follow Erith again?

Solution 1:

Torom the dog is one of the characters that suffers from having unique script commands that tell him what to do. This leads to buggy behavior, since one-off scripts aren't tested nearly as extensively as those for other NPCs.

Torom's known for remaining behind without Erith, as well as oddities like falling out of the sky when you exit a cave and dying. Since he's not key to any quests, nobody's ever really fixed him. I recommend fixing him with a mod, but you can try console commands.

kill and resurrect can be used to get an NPC back on task, but they can also set flags in the game which dictate that a character has died and therefore change certain quests or interactions. resurrect on its own is usually pretty safe, and can restore broken scripts for NPCs.

Personally, I recommend a mod known as AFT, short for (I think) Amazing Follower Tweaks. This lets you do things like have multiple followers and, more importantly, set their home. This way, you can set Torom's home for him and he'll wander around the house where Erith lives.