I'm confused on the attack phase of this game. If a player has no weapons does that mean I have to find a combat card that says no weapon or does having no weapon only effect the damage output, for example if they pass it says "weapon damage +X" if they have no weapon do they essetianlly just do the +X damage?

Also are they allowed to choose what type of attack or strictly what comes up first?

Also for monster attacks and evasion tests, when am I allowed to do these? I understand when a investigator is trying to run pass they have to do a evasion test but do they have to do this by just being in the room every turn?

If you're attacking a monster without any weapons you just draw from the appropriate combat deck untill you draw a card that states 'no weapons', then resolve what's on it. Simple as that. Such cards will never say 'weapon damage + x' but will most likely involve you adding or substracting from your strenght.

As a keeper you can only attack those players who are in the same space as one of your monsters. You can attack during your 'monster attack step'. Unless your monster is stunned of course. Then you simply remove a stun token during this step.

Players only have to evade the monsters in their space when trying to move away from that space. They do this before moving or trying other non-attack actions.

Hope this helps. Happy hunting.