Elephant

The elephant as ally is the war beast, the caravan workhorse, or the druid's Conjure Animals pull. The most common framing is a mounted PC, since the SRD allows Large or larger beasts to be ridden by Medium creatures and the elephant comfortably carries one rider plus howdah. Sketch the relationship before the first fight: this is a trained mount with a name, a mahout's worth of training cues, and a temperament that breaks under fire from spellcasters.

In combat, the elephant is a mobile platform. The rider gets attacks from a 12-foot vantage, the elephant uses its Action to attack on its own initiative, and the 40 ft. speed lets the pair reposition aggressively each round. Drive the elephant through enemy lines once for the dramatic opening, then turn it into a redoubt: park it next to the cleric, have the elephant intercept anything that closes, and use its 22 Strength to grapple the heaviest threat the party can't otherwise pin. The lack of any special action means the elephant is best used as a wall, not as a damage dealer.

Out of combat, the elephant is a logistics solution. It carries gear no horse can lift, breaks down brush at 40 ft. per round, and intimidates village guards into letting the party camp wherever they want. Treat the cost of feeding it as a session-to-session line item.

When the elephant dies, the rider gets a check to dismount safely or take the falling damage. Make the death a beat, not a footnote.

An elephant is a charging tank with no actions block, which is the whole point. The stat block lists Multiattack, Gore, and Stomp on most published versions, but the SRD entry you're running is bare: AC 12, 76 HP, Str 22, Speed 40 ft. Treat it as a generic Huge beast attack at +6 to hit for roughly 18 to 22 bludgeoning, and lean on the Trampling Charge variant only if your table has agreed to use the older PHB-era rule. Otherwise the elephant just runs into things and they fall down.

Run elephants in herds, not solo. A single elephant on a CR-4-appropriate party loses a slugging match because it has no reach beyond melee, no ranged option, and no condition that pins the rogue. Three of them in formation across a savannah path is a real encounter: spread out so the cleric can't single-target heal, charging from outside the party's first-round range, and using the 40 ft. walk speed to push past the front line and trample the back rank. A passive 10 makes them easy to ambush, but once aggressive they cover ground faster than most parties can reposition.

Damage distribution is simple. The elephant goes for whoever is closest and biggest, because it does not think tactically. If the party has a horse or a familiar mount, the elephant attacks that first. The animal handling reads as territorial, not malicious. If the party retreats out of the herd's range, the herd stops chasing.

The elephant doesn't survive long against organized magic, so don't make this fight about depleting HP. Make it about the stampede getting through the village behind the party. The clock is the houses, not the herd.