I'm not sure if you'll be around to read this, but I managed to beat Olumbe by spamming the field with valkyrie, that other valkyrie clone, and that one voodoo guy who summons a thorn bush. Poison really screws you up, so you want to have people who are either tanky (like vampire or paladin) or someone who can buff up your main attackers so they can get a shot in before they die. Even then I still only won by a hair. If you have that one orange card that deals 10 damage to all units on summon she's pretty good, but even still the only way you're going to win is by spamming the field with as much monsters as you can to soak up the poison damage, and having a few other main damage dealing cards to boost you out of the hole.