Can you counter your own spell?
Yes, you can counter your own spell.
According to RiftJudge FAQ #453, Riftbound card text is literal: if a card says "counter a spell" without specifying "enemy spell," it can target any spell, including your own.
Important considerations:
- Targeting: You must have a valid spell on the chain to target. As noted in RiftJudge FAQ #5039, you cannot play a counter effect if there is no legal target on the chain.
- Costs: Per Rule 425.1.c, countering a spell does not refund any costs (energy or power) paid to play it.
- Game State: Per Rule 425.1.b, a countered spell is not considered to have been played. This means any "When you play a spell" triggers associated with that spell will not occur (see RiftJudge FAQ #2705).