Quake

Requires attunement. When you hit an creature while on the ground with this weapon, as a bonus action you may cause the earth to quake. Flip a coin or roll 1d2. On heads or 1, the wielder causes the earth to shake, and causes the effects of the earth tremor spell at 2nd level with a range of 30 feet around you. The DC for this effect is 14. On a tails or 2, the weapon deals 1d8 additional bludgeoning damage. This ability can only be used once, and this weapon regains use of this effect at dawn.