Can Repulse stop Hidden Blade and Cull of the Weak?

To determine if Repulse can stop Hidden Blade or Cull the Weak, we must compare the specific targeting requirements of each card.

Summary

• Repulse vs. Hidden Blade: Yes, Repulse can stop Hidden Blade, provided it targets the same unit.
• Repulse vs. Cull the Weak: No, Repulse cannot stop Cull the Weak because it does not target.

Analysis

1. Repulse vs. Hidden Blade

Repulse is a [Reaction] that states: "Choose a friendly unit at a battlefield. Counter an enemy spell or ability that chooses it and no other friendly unit."

• Hidden Blade instructs you to "Kill a unit," which means it chooses that unit as a target.
• If your opponent plays Hidden Blade targeting your unit, that spell is choosing exactly one unit.
• Verdict: Because Hidden Blade targets your unit and no other friendly units, it meets the requirements for Repulse. You can play Repulse, choose that same friendly unit, and counter the Hidden Blade.

2. Repulse vs. Cull the Weak

Cull the Weak states: "Each player kills one of their units."

• Cull the Weak does not target. The instruction to kill a unit is not a choice made when the spell is played; rather, the choice of which unit to kill occurs during the spell's resolution.
• Because Cull the Weak does not choose a unit as a target, it fails to meet the requirement of Repulse, which only functions against spells or abilities that choose a unit.
• Verdict: Cull the Weak cannot be countered by Repulse.

Timing and The Chain

In both cases, these interactions take place while the spells are on the chain:

1. Playing the Spell: Your opponent plays the spell. It is placed on the chain.
2. Reaction:
   • If the spell is Hidden Blade, you may play Repulse to counter it.
   • If the spell is Cull the Weak, you cannot play Repulse as there is no target to choose.
3. Resolution: If a valid reaction is played, it resolves first, countering the original spell. If no valid reaction is played, the original spell resolves according to its text.

Note: I could not fully verify this ruling against the retrieved rules.