Based on what we know about the Black Order roles, we can piece this together about Proxima Midnight, the lone maf along with Thanos (GF). The description is just copy and paste from Wikipedia.
Feel free to correct anything here. More coming.
I went into detail here simply based on Goon's descriptions of the three that were killed.
Townie - Cull Obsidian, Mafia Janitor: You are Cull Obsidian, the most powerful warrior in the Black Order. As a savage warrior, you have the ability to completely extinguish someone without a trace. As such, should Thanos acquire
5 Infinity Stones, you will gain the
one-time ability to enhance the nightly mafia hit and prevent the player’s role from being revealed to the town. The role will be revealed to the mafia team. The player’s character will still be revealed to the town. If your team chooses to use this power, you must make the hit.
Tim - Ebony Maw, Mafia Roleblocker/Silencer: You are Ebony Maw, member of the Black Order. You have powerful telekinetic abilities that allow you to control most of your surroundings. This control allows you to operate as the mafia roleblocker. During a night phase, you may select a player that you would like to block from performing all actions. This ability has a one-night cooldown (i.e., you may not use it on consecutive nights). Additionally, if Thanos is able to acquire
4 Infinity Stones, you will gain a
one-time silencing power. During a night phase after Thanos acquires a 4th Infinity Stone, you may select a player to silence. That player will only be allowed to post once during the following day phase and the post may only contain a vote for a player. If your team chooses to use this power, you must be the one who silences that player.
????? - Proxima Midnight, Mafia ????: You are Proxima Midnight, a prominent member of the Black Order. Your spear is capable of drastic harm based on how it is thrown and who it is used against, becoming a multi-pronged lance of poisonous energy that follows their target, never missing. As such, should Thanos acquire
3 Infinity Stones, you will gain the
one-time ability to [insert power here] against a player. If your team chooses to use this power, you must make the hit.
toogs - Corvus Glaive, Mafia Strongman: You are Corvus Glaive, a powerful warrior in the Black Order. Your blade is strong enough to pierce through vibranium, a valuable tool when fighting against the Avengers and their allies. As such, should Thanos acquire
2 Infinity Stones, you will gain the
one-time ability to enhance the nightly mafia hit and make it an unblockable hit against a player. If your team chooses to use this power, you must make the hit.