[quote=@GodOfWar]
Depends on the perquisites needed to summon the [i]Hell-forged Blade[/i]. Can Heretic willfully summon it whenever he wants, or will you be maintaining when he can summon it? Such as when he's [b][i][i]Demonized[/i][/i][/b] and what-not.
[/quote]
It wouldn't need to be summoned at all, since it was an SMG melted down and reforged by Kharn while he was possessing Heretic. Currently it's lying on the rooftop waiting for someone to claim it, although its demonically infused metal would probably burn the hand off of anyone other than Heretic who tries to touch it.

For 1 Skill Point Heretic could claim the blade and get a +4 Attack bonus, but could be forced to drop the blade at any time. The blade would be Mystically-powered though, so would be indestructible by conventional means, so Heretic could always pick it up again after dropping it.

For 3 Skill Points Heretic could [i]Soulbound[/i] the blade, allowing him to instantly summon it back to his hand without needing to spend an action whenever he drops it or it's taken from him.

For 2 Skill Points you could take it as an ability, as you suggested, but it would only take 1 Energy/Turn to maintain the blade, rather than 4. If you use this option the weapon would still be classed as [i]Soulbound[/i], since Heretic would be spending Energy to maintain the blade and so it would be permanently tied to him.

With the [i]Armed[/i] status effect you get the limit that you can't use targeted abilities on opponents while [i]Armed[/i], but since you don't have any targeted abilities which would need to be used that shouldn't be a problem.