Quest: Defeat every AI.
This will take a lot longer than most quests, as there are 144 level 5 AI's.
Reward: Rare weapon of your choice, or 6000 electrum.
The reason for this is that many people choose a "useless" weapon when they first get to choose one. Sure, rare farms are common now, but certain farms aren't. Really the only other decent rewards for a quest that would take this long are electrum and nymphs, and the latter should only be from the oracle only in my opinion. Until you win one there, you'll have to make due with nymph tears. Electrum is an option because people that already have multiple of every rare weapon would probably rather have electrum, and four upped cards worth is pretty nice (and I think that amount is what you get for winning tournaments).