Just confirming: cards in your hand are generally considered blank unless the text is relevant.

So my current assumption is that:

1. Loyal Guard when played as a dupe is a textless card, and thus can be played and used on the Viper (despite his immunity to character abilities... since during this transaction Loyal Guard is not a character).

2. Bannermen: 1.) I believe you can play them on the viper from your hand since at that point they are never an actual character. Now when they are in play, could they be played on the viper since their ability turns them into an attachment? (I currently don't think you can... since they are a character when triggering the ability, one would have to choose a legal target before they turn into an attachment.) However once an attachment on another character I think they can be triggered and attached to the viper at that time since he is not immune to attachments.

bloodycelt said:

The are not considered blank. But their text, traits, etc. are considered inactionable unless there is a specific reference to the cards in hand (by the "only cards in play are actionable unless otherwise specified" rule).

bloodycelt said:

Both of these questions are moot because neither card text is acting directly on the Viper. His immunity does not come into play.

1. Loyal Guard's text/effect is self-referential, so obviously, it acts on itself, not on the Noble character it becomes a duplicate of. There is nothing for the Viper to be immune to here.

2. Same thing with the Bannermen. Their direct action is upon themselves, changing them into attachments. So whether triggered from your hand, from play as a character, or from play as an attachment, the Banner's effect is on itself and since it does not "choose" the character it becomes attached to, the Viper's immunity is not relevant. Just like an event or character ability that takes attachments off of a character can discard things attached to the Viper (provided it does choose the Viper, of course), an event or character ability that puts attachments on a character can add things to the Viper (again, provided it does not choose the Viper while doing so).