If my opponent has no Weakness and I use Spiritomb's "Ticking Terror" attack, will I do extra damage on my next turn due to Weakness?
If a Pokemon has no Weakness printed on the card, Ticking Terror will give that Pokemon a x2 Weakness to Darkness.
Source: Brilliant Stars FAQ; TPCi Rules Team (2022-02-24)

Relevant cards

Note: All applicable cards may not be listed below.
SWSH9_89
SWSH9_89