603.3b If multiple abilities have triggered since the last time a player received priority, each player, in APNAP order, puts triggered abilities he or she controls on the stack in any order he or she chooses. (See rule 101.4.) Then the game once again checks for and resolves state-based actions until none are performed, then abilities that triggered during this process go on the stack. This process repeats until no new state-based actions are performed and no abilities trigger. Then the appropriate player gets priority.
You control all the abilities, so you choose their order.
You'll need two Overlords to do your combo with one in the graveyard already. When Knell's ability goes on the stack, you have to declare a legal target. You don't sacrifice anything until that ability of Overlord resolves.
I want to see Demon Possession like a duo monster. Have someone like Nyx from Queen's Blade carry around an ancient demon in the form of a mage's staff and she's subservient to it.
The problem I can see is that Succubi themselves can be done in any other creature type. Roughly they are demons or some other supernatural force that drains energy from men through the use of sex. The game can do it as a Vampire or any other creature types that prey. They can do female demons and just avoid doing to humanoid female body build.
The direct 5 damage is decent, but I would have preferred the choice of dividing the damage.
Ravnica is the main plane with shops.
Dungeons are on various planes.
Player characters are walkers.
NPC are summoned creatures controlled by AI.
Players go through dungeons battling creatures of various colors. Legendary creatures can be bosses.
You control all the abilities, so you choose their order.
You'll need two Overlords to do your combo with one in the graveyard already. When Knell's ability goes on the stack, you have to declare a legal target. You don't sacrifice anything until that ability of Overlord resolves.