General questions

[Rork]

1. On Merlassar there's a puny Elf hero, Guildencrantz. Is he associated to any quest of bounty given later in the game? I'm right past Demonis and I'd like to know if he can be taken out with no consequences.

2. I have a fully upgraded Archmage Staff. Two of its bonuses read as follows:
+5% Stamina Spells
+15% Stamina by Lightning
What does this mean?

3. For those who have completed the game, after the first fight with Guilford, is there a later way to go back to Demonis and Hades? As can be seen from the Demonis map I've attached, more than half of this realm can't be explored. Is this intended (you know, it's not a bug, it's a feature ), will it open at some later stage of the game or is it a, well, bug?

4. In Hades, the flying platform near the entrance from Demonis takes you to a rocky place where there's an inaccessible location called Corrupted Sanctuary (see screenshot). Another feature/bug or will it open later in the game?

Some quick answers, esp. to 3. and 4., would be much appreciated, as I'm postponing the Guilford fight (and any game progression) in order to use the Demonis gate. If Demonis indeed becomes inaccessible after this battle, it means that any demon creatures/items you might need have to be bought now.