Is it really bad to select a plot deck in a campaign that you can't summon the agent.

I was thinking about using Rylan or Tristayne in the Nerekhall campaing.

But I'm not sure if it's a good idea since they both have summon restriction.

Will I miss something important?

it's more for thematic reasons.

I meant on the strategic side, is it really important to be able to summon the agent. Or, I can just use the plot deck and be happy with that.

Is summoning the apogee of the plot deck?

I am not an expert with the plot decks, but I think the Agent summoning is often just a cherry on top of the sundae, and not completely necessary to use the rest of the deck effectively. It just means you have one less thing to spend your threat on.

Agent summoning is typically one of the weaker uses for the plot cards. It's threat heavy (especially since you return the card to the deck and have to buy it again if the agent falls), trades monsters for the agents so it's not a noticeable power boost, and other issues. It's mostly thematic.

I do agree that unless you can ensure that your Agent survives, you'll end up spending a lot of threat for a one time use. That does however change with Skarn as much of his deck is all about summoning him every quest. Looking forwad to that.

I played the whole SoN campaign with the Aleric Farrow plot deck and did not once summon him; I spent my threat on other things like the Dark champions Card. Certain plot decks focus far more on cards than the actual lieutenant. For decks like Mirklace or Queen Ariad, summoning the monster is kind of the whole point, but I think that using Rylan or Tristayne in SoN would be fine.

Another point to summoning the agent version of your selected plot deck could be used as a good distraction so the Overlord can focus primarily on the objective.

My first impressions would be that heroes see the summoned agent as a major threat and would focus-fire on him/her ignoring what they should really be doing in that encounter/quest. Secondly, summoning the agent is a balancing process, if you're using one of the 1x1 base agents, you'd be better off replacing base-like open groups as well. For example, Alric for a Beastman, or Valyndra for a giant or other dragons.