our game is a revolving dm type and weve ran into a problem. Our storm wardens librarian has been given a relic claymore, but he also took sig gear storm shield, I cant find any rules on using two handed weapons in one hand, in DH wasnt there a penalty for such a thing? Recoil suppression only applies to basic weapons, not melee weapons.

Tunnelhckrat said:

You can't use two handed weapons in one hand. If you could; they'd be one-handed weapons...

Strictly RAW, its impossible.

As a house rule, I would allow it, forcing the untrained penalty (like -30 to hit), and subtract 1d10 damage to represent the weaker swing.

Also, probably disallow parry, and impose other crap depending on nature of artifact.

In other words, tell the player to not do that, but allow them if they are stuck on doing it. I would allow them to turn the sig wargear back in for xp, as that was a very poor decision.

He could use a combat shield instead. He could even use it to parry as long as the claymore is not unwieldy.
I just got an official answer about that topic (twohander and combat shield)