Every ogre that gets killed by Ogresmasher gives it a “charge”, which is separate from enchantment. Charges can either grant it damage bonuses, or there is something you can do by applying Ogresmasher to expend charges for a unique effect.

You can apply Ogresmasher to an adjacent vacant space to smash it into the ground and create a pit there. This burns excess nutrition approximately in line with jumping.

If there’s a monster on the targeted square, this just attacks it normally.

Ogresmasher can knock back (possibly entire groups of) small monsters it hits.

Ogresmasher doesn’t need bonuses versus ogres, or confer beneficial properties. It is simply an oversized sledgehammer with such terrible crushing power that it splatters anything it’s swung at. On top of modest damage bonuses, it has chances to instakill sufficiently small monsters, and may inflict negative status effects on large monsters like stunning or slowness (or bleeding, if that is implemented). Probably better if war hammers are made into two-handed weapons.