So was toying around with new design space at work and thought this could be pretty fun. The idea of your creatures acting as double agents or spies or the like. Sometimes it might be better to cast an undercosted body at a downside, sometimes you rather pay a cheaper infiltrate cost and later have to pay to get the creature back under your control, etc. Here's the mechanic itself, some cards using the mechanic and a card that's built around/enables the mechanic.
Infiltrate (cost) (You may cast this for its Infiltrate cost. If you do, it enters the battlefield under an opponent's control and gains "2B: This creature's owner gains control of it. Only it's owner may activate this ability.")
Shadowsleuth Assassin
B
Creature - Human Assassin (U)
When ~ ETBs, sacrifice another creature you control.
Infiltrate 1B (You may cast this for its Infiltrate cost. If you do, it enters the battlefield under target opponent's control and gains "2B: This creature's owner gains control of it. Only it's owner may activate this ability.")
2/2
Information Gatherer
U
Creature - Human Rogue (C)
When ~ enters the battlefield, reveal your hand.
Infiltrate UU
0/4
Thoughtretch Prowler
1B
Creature - Human Rogue (U)
When ~ enters the battlefield reveal your hand. Target opponent chooses a nonland card from it and you discard that card.
Infiltrate 2B
3/2
Shadowsleuth Doppelganger
2UU
Creature - Shapeshifter (R)
You may have ~ ETB as a copy of a creature on the battlefield.
Infiltrate U
0/0
Network of Shadows
1U
Enchantment (R)
Creatures you own have Infiltrate, where the Infiltrate cost is equal to their CMC.
Whenever an opponent draws a card, if they control a creature you own, they reveal the drawn card to you.
"There are no secrets we don't already know."
Shadowlseuth Pickpocket
U
Creature - Human Rogue (R)
Infiltrate 1U
When you gain control of ~, if you are it's owner gain control of target artifact its previous controller controls.
2/3
Sower of Agony
1B
Creature - Human Rogue (R)
At the beginning of your upkeep, you lose 2 life.
Infiltrate 2B
3/3
Note: These were more proof of concept than anything else, and also designed at like 4 or 5 in the morning while I was at work, so numbers may need adjusting as far as costs and balancing and etc.
How i feel about competitive players and casual players in EDH: The competitive are german tourists, the casual are italian tourists, both in a italian beach. The italians asking themselves "why are the germans here?" make a legitimate question, the answer is because the beach is beautiful, no matter the country you came from. The italians wanting to ban the germans are dumb, because if the germans pay for their stay and follow the rules like everyone else, they have the right to be in the beach. Hovewer, if the germans started to ask themselves "why are the italians here?"... they would be dumb as hell.
This seems like narrow design space. I doubt the infiltrate for cost reduction cards are going to be very fun and I don't there's room for many of the upside designs.
Infiltrate (cost) (You may cast this for its Infiltrate cost. If you do, it enters the battlefield under an opponent's control and gains "2B: This creature's owner gains control of it. Only it's owner may activate this ability.")
Shadowsleuth Assassin
B
Creature - Human Assassin (U)
When ~ ETBs, sacrifice another creature you control.
Infiltrate 1B (You may cast this for its Infiltrate cost. If you do, it enters the battlefield under target opponent's control and gains "2B: This creature's owner gains control of it. Only it's owner may activate this ability.")
2/2
Information Gatherer
U
Creature - Human Rogue (C)
When ~ enters the battlefield, reveal your hand.
Infiltrate UU
0/4
Thoughtretch Prowler
1B
Creature - Human Rogue (U)
When ~ enters the battlefield reveal your hand. Target opponent chooses a nonland card from it and you discard that card.
Infiltrate 2B
3/2
Shadowsleuth Doppelganger
2UU
Creature - Shapeshifter (R)
You may have ~ ETB as a copy of a creature on the battlefield.
Infiltrate U
0/0
Network of Shadows
1U
Enchantment (R)
Creatures you own have Infiltrate, where the Infiltrate cost is equal to their CMC.
Whenever an opponent draws a card, if they control a creature you own, they reveal the drawn card to you.
"There are no secrets we don't already know."
Shadowlseuth Pickpocket
U
Creature - Human Rogue (R)
Infiltrate 1U
When you gain control of ~, if you are it's owner gain control of target artifact its previous controller controls.
2/3
Sower of Agony
1B
Creature - Human Rogue (R)
At the beginning of your upkeep, you lose 2 life.
Infiltrate 2B
3/3
Note: These were more proof of concept than anything else, and also designed at like 4 or 5 in the morning while I was at work, so numbers may need adjusting as far as costs and balancing and etc.
UBBreya's Toybox (Competitive, Combo)WR
RGodzilla, King of the MonstersG
-Retired Decks-
UBLazav, Dimir Mastermind (Competitive, UB Voltron/Control)UB
"Knowledge is such a burden. Release it. Release all your fears to me."
—Ashiok, Nightmare Weaver
Yeah. Wasn't positive on the number to go with on it as far as balance goes, but I did want to keep it consistent and make it black.
UBBreya's Toybox (Competitive, Combo)WR
RGodzilla, King of the MonstersG
-Retired Decks-
UBLazav, Dimir Mastermind (Competitive, UB Voltron/Control)UB
"Knowledge is such a burden. Release it. Release all your fears to me."
—Ashiok, Nightmare Weaver
RUNIN: Norse mythology set (awaiting further playtesting)
FATE of ALARA: Multicolour factions (currently on hiatus)
Contibutor to the Pyrulea community set
I'm here to tell you that all your set mechanics are bad
#Defundthepolice