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Spell interruption and Protection

From UO:PvE Wiki

Moving while casting is allowed, but damage and equipment changes can still interrupt a cast.

Development source reviewed on 29 October 2026. In-game availability is unverified.

What interrupts casting#

A player currently in the casting phase receives an interruption check when hurt. Without Protection, that check interrupts the cast. Changing equipment while casting also disturbs the spell. Using an object while a spell is in its targeting / sequence phase can cancel that sequence.

The configured current-era damage-interruption recovery is zero; ordinary completed casts still use their normal recovery timer. Monsters and pets do not use the player hurt-interruption branch.

Protection and school conflict#

Protection places a protection value P in the interruption registry: P = trunc(1000×Magery school strength). At full Magery strength P=1000 and ordinary damage does not interrupt through this check. School conflict reduces P.

For P below 1000 the code interrupts when a random integer 0–999 is greater than P. Exact chance = max(0,999−P)÷1000. At 50% school strength, P=500 and the interruption chance is 49.9%.

Protection costs#

Protection reduces Physical Resistance by 15−floor(Inscription÷20), reduces effective Resisting Spells by 35−floor(Inscription÷20), and subtracts 2 from FC. At 100 Inscription those penalties are −10 physical resistance and −30 Resisting Spells. The penalties remain even when school conflict weakens the protection benefit.

Protection applies to spell interruption. It does not protect a bandage from the shard’s incoming-damage cancellation rule.

Source notes

Show 7 references

These references identify the reviewed shard files. Source presence does not establish live availability.

  1. Projects/UOContent/Spells/Base/Spell.cs:86
    Damage interruption and integer roll
  2. Projects/UOContent/Spells/Base/Spell.cs:120
    Equipment and object disturbances
  3. Projects/UOContent/Spells/Base/Spell.cs:658
    Current-era interruption recovery
  4. Projects/UOContent/Spells/Second/Protection.cs:138
    Resistance penalties and Protection registry value
  5. Projects/UOContent/Spells/Base/Spell.cs:716
    Protection FC penalty
  6. Projects/UOContent/Items/Skill Items/Misc/Bandage.cs:157
    Bandage cancellation is independent
  7. Projects/Server/Mobiles/Mobile.cs:5977
    Damage callback invokes the caster interruption hook

Category: Character & combat