Honestly have that mentally flagged as one of the easier ones. Granted that has a lot to do with my necromancy numbers, but the stuff I can do isn't by any means unachievable by anyone else. The Hambels are old and their stats reflect that.
Nothing stopping you from targeting your summon. Frankly I don't even know why you're asking about your PC targeting the enemy in order to make your pet stronger. That ability doesn't effect your summoned pet at all. Buff buff buff buff. Slots only matter in stuff like dungeon and endurance runs. Stack dozens or even hundreds on your hapless minion. Wish until reality explodes! Bring heals, bring dis-debuffing (...if it's even possible at levels greater than 80. Gotta admit I haven't checked.) so it can't whittle your defense down to auto-kill point.
Like just start of battle stuff that most people have: the +15,000 to all stats from a single constellation gets even a level 1 summon halfway to matching the Hambelstern, and there's no shortage of buffs you can throw out on that level. I'd be totally shocked if someone *can't* boost a level one summon to at least +150,000 to all stats just from in-stock and Wished buffs.
PC isn't barred from targeting the Hambelstern's summons either, so be prepared to deal with those personally.
Base Element resistances issues dealt with easily via Call Unto Wood or Call Unto Metal, which literally anyone can get thanks to in-stock spells and replicable combos.
...with all that said, though, there IS one possible catch that could screw up any possible strategy:
Automatic Level-Based Combat Advantages
Entities have a (Level - (Target Level + 10))% chance of auto-hitting their targets with the first hit of the first attack they make each round.
Damage dealt by entities equal to (Entity Level - (Target Level + 10))% of the total Damage dealt in each instance of damage dealt by those entities automatically bypasses the Defense of their targets.
Damage dealt by entities equal to (Entity Level - (Target Level + 10))% of the total Damage dealt has an (Entity Level - (Target Level + 10))% chance of being unhealable and unregeneratable except from sources of equal or greater Level to said entities.
If an individual is afflicted with a major negative status effect by a lower-Level source, said individual may, as an irremovable effect, reduce its Max HP by (The source's Level * 100,000) and then replace that major status effect's effect text with the text of a minor negative status effect of its applier's choice (with said status effect still counting as a major negative status effect of its original type for removal purposes). If Charm's text is selected, said major status effect has a 25% chance of being automatically cured at the end of each action controlled by said effect (or at the end of each action skipped due to said control).
An individual possesses a per-round chance of recovering from debuffs from lower-Level sources with a percent chance of recovery per stacked instance equal to (Possessor's level - said effect's source's Level at the time of application), with said recovery chance being checked at the start of each round.
Entities may choose to prevent entities 10 or more Levels below them from obtaining Death Attacks.
If a battlespace contains only entities 10 more more Levels lower than an entity, that entity may target entities in that battlespace.
That stuff has a level difference of 83- which puts the active number at 73% for most of those effects, whiiiich is pretty, uh, yikes for this. Particularly notable for the "unhealable and unregeneratable" bits, there, and is kind of ridiculously unfair for an attrition match we're stuck in. (Sidenote: does that accrued damage go away if your pet dies and allow you to resurrect it? Maybe need to post that someplace Gad can see)