Spawning and removing HyperMobs

effectspawn mythic mob <name> at <location>HyperMobs

Spawn one of that mob

spawn mythic mob "SkeletonMinion" at {arena.middle}

effectspawn mythic mob <name> at <location> level <n>HyperMobs

The same, at a level

spawn mythic mob "SkeletonKing" at player's location level 5

effectremove mythic mobs <name>HyperMobs

Take away every living mob of that kind. Without a name: every mythic mob

remove mythic mobs "SkeletonKing"

expressionlast mythic mobHyperMobs

The creature spawn mythic mob made most recently, to keep in a variable

set {boss} to last mythic mob

expressionmythic mob exists <name>HyperMobs

Whether MythicMobs has a mob of that name

if not mythic mob exists "SkeletonKing":
    send "&cMythicMobs has no SkeletonKing."
    stop

expressionall mythic mobsHyperMobs

A list of the names of every mob MythicMobs has

send "&7MythicMobs has: &f" + join all mythic mobs with ", "

expressionmythic mobs aliveHyperMobs

How many mythic mobs are alive now

send "&7%mythic mobs alive% mythic mobs are left."

expressionmythic mobs alive of <name>HyperMobs

The same for one kind

if mythic mobs alive of "SkeletonMinion" < 5:
    spawn mythic mob "SkeletonMinion" at {arena.middle}

Guide and examples

command /summonking:
    permission: "bosses.spawn"
    players only: true
    trigger:
        if not mythic mob exists "SkeletonKing":
            send "&cMythicMobs has no SkeletonKing."
            stop
        spawn mythic mob "SkeletonKing" at player's location level 5
        set {boss} to last mythic mob
        send "&aThe Skeleton King is here, at level %mythic level of {boss}%."

every 10 minutes:
    if mythic mobs alive of "SkeletonMinion" < 5:
        spawn mythic mob "SkeletonMinion" at {arena.middle}

command /clearbosses:
    permission: "bosses.spawn"
    trigger:
        remove mythic mobs "SkeletonKing"
        send "&7%mythic mobs alive% mythic mobs are left."

Syntax	Effect
`spawn mythic mob <name> at <location>`	Spawn one of that mob
`spawn mythic mob <name> at <location> level <n>`	The same, at a level
`remove mythic mobs <name>`	Take away every living mob of that kind. Without a name: every mythic mob
`last mythic mob`	The creature `spawn mythic mob` made most recently, to keep in a variable
`mythic mob exists <name>`	Whether MythicMobs has a mob of that name
`all mythic mobs`	A list of the names of every mob MythicMobs has
`mythic mobs alive`	How many mythic mobs are alive now
`mythic mobs alive of <name>`	The same for one kind

A name MythicMobs does not know is reported in the console and nothing is spawned.
A mob kept in a variable is an entity like any other: health of {boss}, teleport, make {boss} target player and the rest of HyperScript work on it.