This maul is clearly ancient, its was obviously forged by a master and imbued with the Light. What is strange is that the hammer is of Titan make, but when asked, Mairla only confirms that suspicion by answering, "I found it awhile back in an old temple dedicated to the keeper Tyr". It does have a striking resemblance to old descriptions of Tyr's own hammer, "The Silver Hand", but it was clearly forged in honor of that weapon. On top of that, it was likely wielded by a champion of Tyr.
Regardless, it is a mighty weapon forged of a mix of thorium, titansteel, and mithril. But despite that, Mairla wields the weapon without much effort. Likely due to enchantments placed on the weapon. One side has Tyr's Silver Hand engraved into and the other side has the engraving of a helmet. On the hand is the titan rune for "Honor", on the helmet the rune for "Guard". Hence why Mairla calls the weapon "Honorguard".
In my own Homebrew, for 5e, it'd be a +3 Maul that requires attunement by a Paladin and acts as both a Holy Avenger and a Defender magical weapon.
Meaning Undead and Fiends take a bonus 2d10 Radiant damage, the bonuses can be interchanged for AC, and the wielder has an aura of magic Resistance/advantage.