Extra Skill Lock

Extra Skill Lock is an effect that invalidates all Extra Skill effects on the target, including Elgif Extra Skills. Currently, this effect is exclusive to enemy skills.
Extra Skill Lock cannot be cleansed by any means outside purging them.
Leader Skill Lock and Sphere Lock serve as two other counterparts to Extra Skill Lock.
==Colosseum==
While not implemented as a buff, Extra Skill Lock effects can passively appear in Colosseum as one of the Random Rules.
==Elemental Synergy: Nova==
Extra Skill Locks can be negated and purged through the use of the Elemental Synergy, Nova.
==Interactions with Unit Type Bonus Skills==
Since Unit Type Bonus Skills are considered Extra Skills, Extra Skill Lock effects can invalidate Unit Type Bonus Skills.
==Interactions with Player/Summoner EXP Effects==
If a unit with Player or Summoner EXP Effects is affected by Extra Skill Lock, the player will still receive the benefits of the EXP effects regardless.
This also means units, such as Sweet Harlequin Ellie and Sparkslinger Kagiya, can still provide Summoner EXP effects on their Extra Skill even if Fire element is not fully max leveled.
==In-Game Descriptions==
Buff 	Namespaced ID 	In-Game Description
Null EX Skill	DESC_BUFF_NULLES	Extra Skills are null.