Spearwall is a tier-3 shield in terms of statistics. It can be acquired be defeating the large man Diuri in the Monsters in the Marsh quest. In case the wielder stands adjacent to a hex occupied by an ally, the blocking percentage increases by 10 percent-point.
Spearwall will probably be used until the end of the game due to its good statistics.
This sturdy pine shield is noticably larger than most shields you've seen. You got from the body of Diuri, the youngest of the monstrous brothers who had been terrorising the marshes near Ribe.