Mythic Twin Kukris

[MonkeySage]

These mithril kukris, Dawn and Dusk, were created by the Sun God to be wielded by a champion.

I sort of have their properties as individual weapons figured out;
Dawn has both Keen and Speed.

Dusk has Furyborn.

I have the idea that when wielded together, they possess a more potent ability, but I'm not sure what.

I'm wanting it to be a sign of the Sun God's powers.