How do I kill a water queen with a medusa shield?

[Ironhawk]

There is no level of MR which makes a unit invulnerable to the single-target insti-kill/disable spells. As zeldor has found even high 20 MR is not enough to protect you. The problem is severely compounded by the fact that SCs are usually the only prime (size 6) candidate for the many enemy mages to target since those spells favor larger targets.