Not a fast strategy, but it allows for a level pet with low health requirements (Beast: 664HP, non-Beast: 443HP, Elemental: 295HP).
Works with a P/P Blazehound. With a S/B you likely have to add one Bite after the second Puppies with Corporal, and the RNG risk (see below) is higher.
RNG with Clamp:
It can happen that Squashling is still rooted by Clamp where the description says “release Plant”. Haven’t seen this in a while, but it can happen. We are screwed then. Low prob.
RNG with Blazehound:
The non-crit damage of Obsidian Bite varies between 379 and 705. So, if you are unlucky it may happen that your Blazehound doesn’t bring M-37 into Failsafe. In that case you have two choices: 1) If the leveler XP is important, then restart the fight. 2) If not, then bring in your Squashling (instead of the leveler) after Blazehound’s death: You will then win the fight, but your Squashling may survive and you won’t get XP.