The chimera is a large, mid-level monstrosity whose conglomerate nature is reflected by behavior that thumbs its nose at evolutionary imperatives. According to the Monster Manual flavor text, it has “a vicious, stubborn streak that compels it to fight for the death”; it “often toys with its prey, breaking off an attack prematurely and leaving a creature wounded and terrified before returning to finish it off”; and yet, despite being unable to speak itself and understanding only Draconic, “if offered food and treasure, a chimera might spare a traveler.” Want a monster that puts the “chaotic” in “chaotic evil”? Here you go!
With exceptionally high Strength and Constitution yet merely average Dexterity, the chimera is an out-and-out brute that will close to melee range as quickly as it can; this is reinforced by its Fire Breath feature, which has a range of only 15 feet. Stealth is not in its repertoire, but don’t try to sneak up on it, either: it has a +8 Perception modifier. It has darkvision, so it will often attack at dusk or at night; it may also dwell underground.
Chimeras are stupid (Intelligence 3) as well as brutal. They aren’t the slightest bit choosy about their targets, nor do they recognize whether one player character seems to pose a greater threat than another. They attack whatever happens to be in front of them. That being said, when they first enter combat—with a flying speed of 60 feet—they’ll position themselves, if possible, to catch as many targets as they can within the 15-foot cone of their Fire Breath. If they can’t get at least two, it’s hardly worth it.
The chimera’s Multiattack is a spectacular feature, allowing it to combine its Fire Breath with two melee attacks. Even dragons don’t get to do that. While its Fire Breath is recharging, it gets three melee attacks rather than two. For the sake of flavor, I’d go by the portrait in the MM and say that, if the chimera is fighting multiple opponents, its goat head attacks left, left-forward or forward; its dragon head right, right-forward or forward; and its lion head forward, left-forward or right-forward. (Alternatively, maybe your chimera is “left-handed,” with the dragon and goat heads switched.) Horns are the goat-head attack, Fire Breath is the dragon-head attack, Bite is either a dragon-head attack or a lion-head attack, and Claws have the same attack arc as the lion head.
The feature allows the chimera to substitute Fire Breath for either its Bite attack or its Horns attack, but I’d substitute it only for Bite (a goat head can’t breathe fire—duh!) except in one specific circumstance: when its positioning is such that it has no opponent within goat-head range, but it does have an opponent in lion-head range.
The chimera uses its Fire Breath every time it recharges, as soon as it recharges, and repositions itself, if necessary, to catch the greatest possible number of targets within that 15-foot cone. If possible, it will simply circle one of its current melee opponents to achieve this positioning, but if it has to move, it will do so, regardless of whether this may incur one or more opportunity attacks.
The chimera has Wisdom 14, which I would normally interpret as having a strong self-preservation instinct and a good sense of when to retreat, but the flavor text specifically says chimeras fight to the death. OK, if you say so, Wizards of the Coast. Me, personally, I’d at least give that self-preservation instinct a chance to kick in when the chimera is seriously injured (reduced to 45 hp or fewer). Maybe it has to make an Intelligence check akin to maintaining spell concentration (DC 10 or half excess damage, whichever is greater) to have the sense to take flight and Dash away.
Similarly, if you want to go by the MM flavor text and have the chimera toy with its prey, keep track of your PCs’ hit points, and have the chimera break off when every PC is reduced to 40 percent or less of his or her hit point maximum, then come back half an hour later, before the PCs have a chance to complete a short rest.
Finally, since the chimera’s flying speed is greater than its land speed, it will move by leaping, and it won’t be hindered by difficult terrain. In fact, it may even prefer to live and hunt in difficult terrain, where its prey is likely to be slowed.
Next: An examination of dragonkind.