PyroHydra, LevelUp's version is great - RESULTS after fight

 https://a5e.tools/node/1694

Jason and the Argonauts. This hydra's heads are similar to the figure we have. BTW, thx https://monsterzone.org/2021/12/19/posters-for-jason-and-the-argonauts-1963/

This one is perfect for what I'm looking for, after reading up on others. I own the PDF, and it had a few more important tidbits that are left out on the website, funky. CR13. The party is like level 13 still (going to be 14 after this). 

Highlights:

• 15 ft reach
• 30 dmg kills a head, instead of 25. 
• Legendary Actions
• Wrap (grapple), typically one enemy. DC 17
• Rush, DC17 str, can bowl over enemies and get in their space, push them out. 
• Knowledge check tells you to Cauterize the wound of a hydra (oops, pyrohydras not the same, but lore won't tell you)
• Can't flank it (unless only 1 head)
• Reactive Heads. For each head it has, the hydra can take one reaction per round, but not more than one per turn.

UPDATE: The actual run I did with it:

• One weird thing, it wasn't clear after reading like 5 versions of Hydras, if their bodies were always invulnerable or if only sometimes. I played it 50/50, described it as the first attack on the body seemed to halfway heal up, so then he technically just went for heads/necks. 
• Had to up HP to 300ish b/c the party just does too much single target dmg. Fighter, even worse with action surge. Barbarian with 3 attacks during frenzy, and "Amulet of Hacking". Etc. 
• Probably should have let the nearby fire spouts from wall hit the 
• players
• or hydra
• and if hit hydra, shoulda let it "help him" from being hurt by cold, aka, let him regen a pair of heads. 
• Still only lasted 2 rounds. Well a surprise round + 2 rounds... if it could have survived one big hit at the end, would have gotten its turn again. 
• Was pretty fun, though wasn't that scary. Only the fire attack was scary, but 3 outta 4 of the PCs have fire resist. And the kid guessed right and had a dern frost brand to whip out on round 1, plus used all cold spells. So I let it regen two heads (just so we could see it happen) but it never did after that. 
• Legendary RUSH was cool one time to avoid an AOE plus get next to all 4 PCs (woulda been nice if had fire recharged). Nice that no AoO when using (kinda a major deal), b/c you only want to challenge one non-strength character to get a decent chance of it working... certainly don't want to try to rush down 3 guys and have 3 chances for them to stop you. 
• The Wrap Grapple thing seemed cool but was ineffective. Casters can still cast. And soon someone would do 30+ dmg and knock off a head (that head).