Is there a solution for the "Invincible" keyword in my card game?

[SeekerOfTruth007]

Invincible (Permanents with Invincible can't be affected by anything opponents control.)

I intend this ability to be true invincibility which cannot be over-ridden in any way. However it becomes way, way OP as a permanent keyword, so I'm pretty sure the solution is to only give it to weenies and only temporarily. For example, I THINK it's fair with a double-intense activation cost which then the effect lasts until end of turn before removing itself. The classic example from my set of cards is "Guardian of Forever".

Guardian of Forever SS

Unit - Guardian - R

SS: Guardian of Forever is Invincible until end of turn.

2/2

I find this ability on units bigger than 3/3 becomes problematic, and a guy on Quora correctly told me nothing should have true invincibility. Well, temporary invincibility might solve the problem if I put it on weak enough combat units.

Updates

1 y

Another solution, since even temporary invincibility is OP sometimes, is to have the Temporary Invincibility "self-countering", so the Invincibility will be "less oppressive". Observe:

SS: *This permanent* gains Invincible until end of turn. Any opponent may counter this ability by paying 3.

[Ez-Bri-Z_v2]

Sacrifice might work.

They aren't being targeted by the opponents cards, the player is. It all just depends on how you write the rules, I suppose.

[SeekerOfTruth007]

I get where you're coming from, but right now the only sacrifice abilities are those of the bad guy, Xyxyl, who sacrifices his own henchmen to try to gain power. The only exception to this is there is a Spirit card which sacrifices itself to save another unit from certain death. thematically, it doesn't make sense for Spirit to use sacrifice except self-sacrifice.

[SeekerOfTruth007]

Right now i have this card (needs a better name).

Fall Guy 1S
Unit - Soldier - Common
Sacrifice Fall Guy: The next time target unit would be destroyed this turn, Heal it instead.
2/2

[SeekerOfTruth007]

Right now, the bad guy sacrifices creatures other than himself to get powerful effects.

Xyxyl's Profane Altar 3
Tool - Uncommon
1, Sacrifice a Unit: Draw two cards.

[Anonymous]

Awesome.