Mode: Solo (3 player-turn cards, do not lose on exhaust) Nemesis: Gate Witch, probably also works with all other nemeses Difficulty: Extinction (Increased difficulty rules, 8/25/90 starting life for player/Gravehold/GateWitch)
Mage and Supply: Handpick everything using only content from the base games (only AE and AE:WE are allowed, no extensions) Apply the usual supply constraint "3 gems, 2 relics, 4 spells".
Nemesis deck: Gate Witch cards + 1/3/7 basic cards for tier 1/2/3. Use the basic cards from War Eternal.
Expected win rate: at least 40%. I won this on my first try, but was lucky with the nemesis deck. I expect this to be a snowballing game: either you can set up your deck quickly, or you are dead.