1) Can you have more than one active Warlock Quest, outside of the Warlock Quest variant provided with Frostmarch?

Some strangers and events let you accept a Warlock Quest without mentioning any restrictions.

Can you replace an outstanding Warlock Quest with a newly accepted one, or do you simply ignore the card that lets you accept a new one in case you have one already?

2)Just to be sure, when fighting the Lord of Darkness in the Dungeon, it's mentioned that you can't use objects,spells and followers that figt in your place.

Are those merely restricted to summoning spells and such?

zealot12 said:

#1: No, barring variant or Warlock Quests ending in play. If you use the Replace Quests variant, then you can swap a current quest to a new one when you get an encounter offering you a WQ.

#2: Yes. There are at least two Followers (Faithful Hound and Friendly Giant) who can fight in your place in addition to the Summoning Spells.