Perhaps this belongs in the regular game forum, but for me this is specifically for RtL.

Since the last time I played "regular" Descent, I bought a few lieutenants, but I never had the chance to use them. Actually, never even opened their packages. Until now.

I'm considering entering them into RtL as being "owned" for more options, so I opened the packages and noticed that the monster cards for each lieutenant is slightly different from the ones that came with the campaign boxes (the ones associated with the cardboard tokens)

The first thing I noticed is that the free versions of the lieutenants have attributes, and the purchased versions of the lieutenants do not.

Does anyone know the reason for the difference?

How would I use them with RtL?

(Please, keep in mind I don't know how to use them in the base game either)

First, read the rules in the lieutenants packs, this helps to understand the concept of the agent card (the lieutenants cards without attributes and some small differences in stats / skills).

Short version: every plot deck has a specific card to summon the proper lieutenant in a quest, replacing part of a group of monsters (or all group in the case of the large lieutenants). This concept is used in the app as a major peril, a surprise event that summons this agent with some friends to complicate your life . In this case, the app tells yous to use the agent (for example: place the Splig "agent" within five spaces from the hero, with 4 goblin archers adjacent to him ...." ) and they apper in the middle of a round to fight the heroes. Otherwise, the app tells you to use the proper card for a lieutenant ( place the "lieutenant" Lord Merric Farrow in this place ...). Normally the lieutenants (the ones with attributes stats) appears only in the story missions and they are part of the setup at some point of the quest.