I, on the contrary, started by clearing out the Dragon strongholds underground – I needed the Berserk spell, Powerful Blast, and mana doubling, plus I could customize additional skills there, choosing ones that included Rust. Luckily, I had already captured their spawning grounds in the swamp. And I only attacked the Life strongholds after conquering the second Citadel and the Order stronghold in the center, underground.
By the way, I killed the Black Dragon with 10 Titans with the Underworld creature, 1+1 Archdevils, and 1+1+1+1 Gargoyles.
Added 1 minute ago
Kelt was great with the boots and gloves. I gave him Pathfinding and Logistics. He also had Diplomacy; no one else had it.