B2B Live TBC 2.4.3

Schildwache Selarin sollte nach Abschluss der Quests 'Flucht durch Verstohlenheit' oder 'Flucht durch Gewalt' neben 'Terenthis' spawnen und 'Marsch ins Eschental' anbieten.

By kroch (7,417 – 1·11·56) on 2010/04/03 (Patch 3.3.3)

I picked up her quest Trek to Ashenvale today after the following three events:

I completed How Big a Threat?
I picked up How Big a Threat?
I picked up Thundris Windreaver

It was immediately following these three consecutive events that Sentinel Selarin appeared/ spawned at 39,45 right next to Terenthis. They exchanged words. She waited around only for a few minutes, and then she ran off to get a pedicure and to get her hair did/ despawned.

It seems to me that there might be a number of ways to make her spawn and get this quest. All of them involve turning in a quest to Terenthis.

betroffener NPC:
Schildwache Selarin https://tbcdb.rising-gods.de/?npc=3694
Thundris Windwirker https://tbcdb.rising-gods.de/?npc=3649
Terenthis https://tbcdb.rising-gods.de/?npc=3693
Raene Wolfsläufer https://tbcdb.rising-gods.de/?npc=3691

betroffene Quests:
Marsch ins Eschental https://tbcdb.rising-gods.de/?quest=990
https://tbcdb.rising-gods.de/?quest=10752 ( Added in patch 3.3.0.10772 ) !
Flucht durch Verstohlenheit https://tbcdb.rising-gods.de/?quest=995
Flucht durch Gewalt https://tbcdb.rising-gods.de/?quest=994

Quellen:
https://youtu.be/hEWDNjbmTr4?t=12m11s
http://www.wowhead.com/npc=3694/sentinel-selarin#comments
http://wowwiki.wikia.com/wiki/Sentinel_Selarin