The Elder Scrolls: Betrayal of the Second Era · Board game rules
Can Tenacity interrupt resolving rolled dice during an Engage?
Quick answer
Only indirectly: tenacity itself doesn't interrupt anything, but a class ability with the Interrupt keyword that you trigger by spending tenacity can resolve before another ability, including during dice resolution in an engage.
Details
Tenacity is a resource spent to trigger a class ability; it isn't an interrupt mechanism on its own [p.25 — Tenacity]. Whether a class ability can interject into an engage's dice resolution depends entirely on that ability's own timing keyword. If a class ability has the Interrupt keyword, "it may be triggered according to its text's timing, either during a unit's turn or outside battle. If another ability or game effect would be resolved, the interrupt ability is resolved first" [p.25 — Enduring / Interrupt]. So an Interrupt-keyword class ability, paid for with tenacity, could indeed resolve before another effect during an engage's roll resolution, provided its text's timing allows it.
By contrast, a normal (non-Interrupt, non-Enduring) class ability is simply an action you may take "any number of times per turn," but "each non-enduring class ability must be triggered at its correct timing and can be triggered only once per turn" [p.61 — Class Ability]. This means you can't freely interrupt the Resolve the Roll step of an engage (page 60, step 5) with an arbitrary class ability just because you have tenacity to spend — the ability's specified timing governs when it can be triggered.
During the engage's "Resolve the Roll" step, abilities (including your own class abilities, if their timing allows) are resolved one at a time in the order the acting player chooses [p.60 — Resolving Skill Abilities]. If two Interrupt abilities would need to resolve at the same time, the party decides the order [p.25 — Enduring / Interrupt].
Watch out: Simply having enough tenacity does not let you interrupt dice resolution — you must have a class ability whose text explicitly carries the Interrupt keyword and whose specified timing matches that moment in the engage sequence.
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