Do not have more than 1 monster on your field during Marik's main phase, otherwise Marik can special summon Lava Golem. You can turn your toggle to on, and activate Beast Rising before Marik's main phase.
Either I have really bad luck, or something is off. I'm convinced that Lava Golem just won't drop from him (I know, it's random, but still). I used 3482 keys, which works out to about 60 duels. I used an Ojama deck, which actually works quite well (if you know how to play it). Not a single Golem, but I did get 16 Granadora and 12 Humanoid Slime. Ugh...
Do not summon 2 monsters except during your last turn, always fusion summon Ojama Knight to lock 2 monster zones of your opp. If you can't manage to lock 2 zones as he already has 2 monsters on his field, keep attacking so he only has 1 which keep him from tribute summon Des Gardius, as he will use Jeroid to reduce your atk. Good luck bro.
I don't really remember but i think you should summon knight in defense mode and keep it like that till last turn. If i recall correctly, he won't equip mask of the accursed on a 0 attack monster. In last turn you summon 2nd ojama knight in attack, play ojama country switch your 2nd knight to attack and then, you summon vassal, and for nightmare wheel use anti magic arrows.