You can ask a friendly Bard (wink wink) to charm the mobs for you, or you can have someone invis you after you've already opened the trade window. I'm actually not sure whether you can cast spells while a trade window is open, it's just not a situation I'm in very often, so you may have to have someone else invis you.
On this server if the invis is applied while the trade window is open, then you can do the turn-in (I've tried this).
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Project 1999 (PvE):
Giegue Nessithurtsithurts, 60 Bard <Divinity>
Starman Deluxe, 24 Enchanter
Lardna Minch, 18 Warrior
Project 1999 (PvP):
[50 (sometimes 49) Bard] Wolfram Alpha (Half Elf) ZONE: oasis |