You see, this happens to be the forte of the one known as the Nameless Undead Overlord. When in a blind mad melee, the Overlord's reliance on his hefty armor is not such a burden. No foe is going to sit down long enough to concoct a method of penetrating it while they are worried about other opponents. And it seemed most certain that the pyromancer who had never once actually said his name had forgotten all about him. A mistake he would not live long enough to regret. 

The Overlord took about five leaping steps towards him, thrusting his blade backwards to build up momentum at its greatest full swing. As he closed the gap between him and his mystic foe, he enveloped his blade once more in a thick swathe of flame. Usually, this coating of flame would be expelled to fire off a spell. However, Overlord was charging up a new and significantly more powerful spell. Though, since he is in motion and he is about to strike at someone, this spell is going to take quite some time to charge. Likely within the range of 30-40 seconds. 

As he closed the gap, he lunged forward and hefted his weight to the left. Swinging his colossal blade towards the midsection of the pyromancer. A side effect of charging his spell would be an enhanced strike upon his foe. With flames engulfing his blade, it would deal a significant deal more damage than it would with just the blade. Now, this blade is massively heavy. And nigh-indestructable. Should this weapon's swing remain uninterrupted, it will cleave his infernal foe in twain.