Hi. Use a invencible hidden monster, give it use invisible skill and earthquake.
Summon it wherever you want. It will look like the main monster casts the skill.
Example:
\db\re\mob_db.yml
- Id: 3038
AegisName: HIDDEN_MOB7
Name: Monster 7
JapaneseName: Hidden Mob 7
Level: 151
Hp: 10000
Attack: 500
Defense: 200
MagicDefense: 100
Str: 100
Agi: 100
Vit: 100
Int: 100
Dex: 400
Luk: 100
AttackRange: 1
SkillRange: 12
ChaseRange: 12
Size: Small
Race: Formless
Element: Ghost
ElementLevel: 4
WalkSpeed: 1000
Class: Boss
Modes:
Aggressive: true
IgnoreMagic: true
IgnoreMelee: true
IgnoreMisc: true
IgnoreRanged: true
\db\re\mob_skill_db.txt
3038,Hidden Mob 7@NPC_INVISIBLE,idle,353,1,10000,0,30000,yes,self,always,0,,,,,,,
3038,Hidden Mob 7@NPC_INVISIBLE,attack,353,1,10000,0,30000,yes,self,always,0,,,,,,,
3038,Hidden Mob 7@NPC_HELLBURNING,idle,719,1,10000,0,3000,yes,self,always,0,,,,,,,
3038,Hidden Mob 7@NPC_HELLBURNING,attack,719,1,10000,0,3000,yes,self,always,0,,,,,,,
Script
prontera,155,145,5 script Test#bssk03 2362,{
npctalk "Walk close to me in the next 10 seconds and you will burn!";
.@event$ = strnpcinfo(0) + "::OnMyMobDead";
monster "prontera",155,148, "#f_w_1",3038,1, .@event$;
monster "prontera",158,145, "#f_w_1",3038,1, .@event$;
monster "prontera",155,142, "#f_w_1",3038,1, .@event$;
monster "prontera",152,145, "#f_w_1",3038,1, .@event$;
sleep 10000;
killmonster "prontera", .@event$;
npctalk "It's safe now...";
end;
OnMyMobDead:
end;
}