The “Level” in “A Deal with Dark Ruler” is the original Level printed on the Monster Card.
If your opponent’s Level 8 or higher monster than you control is sent to the Graveyard, you can activate “A Deal with Dark Ruler”.
You cannot activate “A Deal with Dark Ruler” during the Damage Step.
You can only Special Summon 1 monster with “A Deal with Dark Ruler”, but you can activate 2 copies of “A Deal with Dark Ruler” to Special Summon 1 “Berserk Dragon” for each, even if only 1 Level 8 or higher monster was sent to the Graveyard.
You can activate “A Deal with Dark Ruler” if your Level 8 or higher monster that is an Equip Spell Card is sent from your side of the field to the Graveyard (such as “Koitsu” or “Dark Necrofear” destroyed by “Heavy Storm”).
Netrep Rulings:
“A Deal with Dark Ruler” may only be activated after a Level 8 or higher monster is sent to the Graveyard from your field.
“A Deal with Dark Ruler” may not be activated in a chain with an effect that would send a Level 8 or higher monster to the Graveyard if a Level 8 or higher monster has not been sent to the Graveyard this turn.
If the summon of a Level 8 or higher monster is negated, “A Deal with Dark Ruler” may not be activated for that monster.
“A Deal with Dark Ruler” may be activated in the End Phase, or the Battle Phase, but cannot be activated in the Damage Step.