Replicating Ring

Some cards have additional effects for each {S} spent to cast them. You can cast these spells even if you don't spend any snow mana to cast them; their additional effects simply won't do anything.

The Kaldheim set doesn't have any cards with mana costs that include {S}, but some previous sets do. If an effect says such a spell costs {1} less to cast, that reduction doesn't apply to any {S} costs. This is also true for activated abilities that include {S} in their activation costs and effects that reduce those costs.

The check of whether Replicating Ring has eight or more night counters on it happens only as part of the resolution of the triggered ability. If Replicating Ring picks up its eighth night counter at another time, you won't immediately create Replicated Rings. You'll have to wait until the next time the triggered ability resolves.