Since Chufmoney was asking how a C&D "character" should be handled, I wanted to throw out a semi-complete design, using, so far as I can tell, 100% existing tech that other characters employ in some fashion. It is loosely based on parts of Doom, Kitty, Vision, and a few other characters.
The basic premise of the design is that one character would be the "lead" character, the one in the center of the screen that you directly control, and the other would be a "partner" character, which would hang by your shoulder most of the time and execute moves. This would be similar to Lockheed, or Loki's clones, or various other semi-permanent sidekicks. Then there would be a toggle that would swap them, allowing you to directly control the second one instead.
Now one element that might be a bit tricky is that I'd prefer that the second character move independently, and that if you use a move with a movement component using Dagger while controlling Cloak, that she would move while he would stay in place, like with Loki's Illusionary Projection, while if you use that move while controlling Dagger, it would be a normal dash move and Cloak would follow behind.
Their default power source would be "Balance", and would have a display a bit similar to Doom's. It would default to half black, half white. As you use Cloak powers, it becomes more black, as you use Dagger powers, more white, and it shifts to neutral over time when not spending resources. Having it nearly maxed to one side or the other would have a penalty, like reduced defense or self damage over time. When you specialize to one character or the other, it becomes a single bar, and behaves like normal Spirit, only the UI is reversed (filling with use, rather than emptying).
Dagger would use Energy attacks, Cloak would use Mental, although if a hybrid is not desired, then all Mental would be best. Their Synergy benefits would be "+damage to Weakness, +damage to Vulnerable"
The three power trees would be Salvation (Dagger), Companions (both), and Void (Cloak).
Attacks/Movement:
Light Daggers (Lv1, Salvation, Ranged, Basic): basic, ranged attack
Reposition (Lv1, Movement, Void): basic teleport, Cloak moves both characters.
Dagger Wave (Lv2, Salvation, Ranged): A fan of light daggers similar to Wave of Arrows. 4s CD.
Swirling Gyre (Lv4, Void, Area, DoT): This would be a 10ft PBAoE channeled ability, slowing and applying a DoT. This would be Cloak's AoE spender.
Lightwheel (Lv6, Movement, Salvation): This would be a movement similar to X-23's Graceful Maneuver, except that it also sends out 2-3 homing ranged darts, similar to how Silver Surfer's Board Dash works. It would be a primary method of attack. Spammable.
Into the Cloak (Lv8, Void, Area, DoT): This sends out a mid-screen distance cone AoE that damages and applies Vulnerable and a DoT to enemies. 4s CD.
Go with the Light/Dark (Lv10, Movement, Companion): The travel power, with Dagger out she jogs, with Cloak out he glides forward, the other character follows along.
Light Barrage (Lv12, Salvation, Ranged): This would be ranged light daggers similar to Scarlet Witch's Chaotic Hex. Spammable.
Darkness Touch (Lv14, Void, Ranged, Area, Basic): Basic short range cone attack.
Dagger Burst (Lv16, Salvation, Ranged): A large single target packet of 5+ daggers, instant cast, 8s CD.
Embracing Darkness (Lv22, Void, Area, DoT): This power sends out a circular wave of darkness to mid-screen, and then returns, dragging enemies with it. 8s CD.
Angeldust (Lv34, Void, Area, DoT): a mid-screen distance cone AoE that damages and applies Weakness and Slow to enemies, and a HoT on allies. 4s CD.
Consuming Void (Lv47, Void, Area, DoT): This power teleports cloak to the target location and causes a 10ft PBAoE that sucks enemies into him and causes him to vanish, dealing damage. Any enemy that takes lethal damage never returns, other enemies reappear at Cloak's location. 8s CD.
Passives:
Castle (Lv1, Companion): Swaps which character you control, 10s CD, includes defensive passives that shifts from Dodge-based on Dagger to Defense based on Cloak.
Seeking the Light (Lv 18, Salvation, Passive): Regeneration, +Crit Damage, edit: active CC breaker
Lost in the Dark (Lv 28, Void, Passive): +Brut damage, self-rez on 10m cooldown
Signatures:
Blinding Light (Lv 30, Salvation, Ranged, Area, Signature): high damage mid-screen PBAoE, applies Weakness and either removes a lot of Dark from the balance meter (making up for heavy Cloak use), or refills Spirit if in solo mode. Also applies a HoT on friendly players. Shared cooldown with Embracing Void.
Seeking Void (Lv 30, Void, Ranged, Area, Signature): high damage mid-screen PBAoE, applies Vulnerability and either removes a lot of Light from the balance meter (making up for heavy Dagger use), or refills Spirit if in solo mode. Also applies a DoT. Shared cooldown with Blinding Light.
Specialization toggle:
Dark Form/Light Form (Lv 42 Companion, Specialization): This has three settings.
In Dagger setting, you can only control Dagger, Castle becomes disabled, the Balance bar becomes a single "Light" bar that fills as you attack and empties over time or through using Dagger's sig. Cloak is not visible by default, but you can still use his spender powers, causing him to appear, use them, and leave, similar to Cyclops' call-ins, but with a doubled cool-down (and cannot use spammables). You cannot use Cloak's Signature.
In Cloak setting, the opposite of the above is true, Cloak is always out, Dagger is not.
In Harmony setting, you play as normal, but receive a significant bonus to damage when Balance is nearly equal, and halves the CD on the sigs (but still shared).
edit:
Ultimate:
- Block Party: I love a good "multi-character army" attack, and who better to deliver it than Cloak? He vanishes and reappears with a half-dozen or so of C&D's friends, Spider-Man, Black Widow, Daredevil, Moon Knight, Luke Cage, Nova, Sunspot, Firestar, there are plenty of characters in game who could make an appearance. They show up, have some fun, then go home. ;)
I think this offers a wide selection of interesting ability options, and would make for a fun character that could be played several different ways. What do you guys think? is it missing something important? Too complicated? Not complicated enough?
Btw, one thing they should keep in mind for costumes is that one of their first alt costumes should be the "negative" versions, which would basically just be pallet swaps of the defaults, so they should keep that in mind when making the default textures, so it's easy to swap. They should also swap the effect colors from black to white, but this should be easier than most color-swaps like Billy's.