What are some of your relic ideas

BabyMiike

Science: maybe a poison champ aka a IBomb relic makes poison more potent
Skill: every time a skill champ purifys a buff increase the purify accuracy by %
Mutant: something to do with bleed would help a lot of champs like Domino etc
Cosmic: something to do with armor break would be very interesting
Mystic: every buff that is neutralized increases power gain effects by %
Tech: increases potency of armor up buffs by %

altavista

I don't think Relics should just be an effect; it should also change mechanics.

Mortal Kombat 1 was just released as has a Kameo system, which seems similar to a Relic (another character that can jump in to do something).

The difference is that the Kameo's add something instead of just extend.

Currently Relics just add a combo extender, or enhance some ability that a champion already has. Sure, Gambit + Gambit relic does more damage from SP2. But that doesn't change anything materially about the fight itself - you are still taking in Gambit for fights where you can gain prowess and do specials. If you are penalized for having buffs or can't use your specials, then the Relic is pointless.

But what if Relics add something to compensate for a weakness or provide a new opening?

Herc can't damage a defender that is immune to physical and direct damage? Maybe have a Captain Universe Relic you can add on that will let you change your damage type to energy for 5 seconds.

Node path has unblockable specials? Maybe have a Unus Relic, where you can block Unblockable attacks for 1 second.

This would be a lot more complicated for Kabam to implement, and would need balancing to make sure there aren't unintended interactions. But relics that do a more than just 5-hit combo extender + some percentage points more to pre-existing abilities, would be a lot more interesting.