Another seemingly easy subject is battle resolution. Well, it is easy in simpler games, like Final Fantasy, but not in XCOM-style games, where you can leave site, without recovering all characters and/or items, or recovering part of them. So there can be no precise victory condition, where you need to just recover that specific alien technology or a specimen, and then retreat. I decided to break player forces into mercenaries and leaders, so player can retreat at any time when his/her all leaders are at the map's edge, or when he defeated all enemy leaders, or when he/she has cast the Spell of Mastery for that specific site. If some of the leaders are not at the edge, they will be lost, but all mercenary units will retreat by themselves. There is a catch to that: player must have at least one leader, otherwise it is an instant defeat (yeah, leaders are akin to lives in arcade games), but leaders require constant upkeep, while mercenaries require larger payment for each battle. Trying to cast the spell of mastery instantly reveals all player leaders to the enemy, and frees AI to use all his many units at once against the player.
Obviously not all sites allow casting the Spell of Mastery, and not all dungeons have leaders. In some cases player just have to recover the quest item or plunder some gold. And if player say starts with a thief, it can gain some quick money by getting inside dungeons, around the guards to reach treasury room, or maybe rescuing some prisoners taken by orcs. I.e. that exact mechanics from the preview demo.