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For fortress sieges and lost vale, you need the wards that they provide, cause now you can't not only not tank them, but also not damage them.
For fortress sieges, Annhilator is sufficient.
Taken from Mythic Entertainment | Warhammer Realm War:
Lesser Ward
Bloodlord Armor Set
Found in: Bastion Stair
Requirements: Ranks: Ranks 37-39
Annihilator Armor Set
Found in: Tier 4 RvR
Requirements: Ranks: Ranks 35-39 and Renown Ranks 31-35
Both sets can be used in any combination to offer the Lesser Ward, which is required for City High Level Dungeons and Fortress encounters. There are five pieces of armor in each set.