I wrote previously about giant beasts in my treatise on essential spirits. You may have different preferences, but I like the idea that giant versions of mundane creatures are mundane creatures that were taken over by a nature spirit and grew to great size and significant intelligence.

Of course, you can always say that some giant creatures are the result of magic of another sort or even just natural to your world. They just need to be rare enough to be fantastical and not, logically, wreck the ecosystem.

Nature

The spirit anchor is a wild beast such as a bear, deer, lizard, beetle, snake, shark, eagle, spider, or lion. The creature grows to very large size and goes from beast to low intelligence, but often exhibits substantial wisdom. The size and intelligence is comparable to the power of the spirit; but the greater the spirit, the greater its desires and ambition.

Such creatures are supernatural versions of their natural counterparts, more intelligent, driven, purposeful, and–often–hostile. Such creatures are often revered and even worshiped by primitive folk, particularly if less hostile.

Because they inhabit a body, they principally appear as a huge version of their mundane selves but often with strange coloration, eyes, and/or paws or hooves (the part of them most in contact with the material plane). They may also project their spirit some distance to appear as a phantom in unlikely places and may attack to terrify.

Giant creatures may be ravenous or vicious or they may be rather quiet and even friendly, but they’re all quite needy in their own way, because they’re driven by desire for psychic energy (from terror, worship, or engaging interaction) more than food or other mundane pursuits.

Reproduction

Being singular and magical, such creatures cannot reproduce naturally, but they can bear giant offspring if already impregnated at the time of possession. This means that any group of giant beasts encountered will always be siblings or parent/child.

But that can include an entire colony of giant ants, termites, bees, etc. that have a perpetually pregnant queen. Such creatures share the original spirit’s energy, tho, and are individually less large and intelligent than a single giant creature. A giant bee from a giant hive might be a foot or so long, while a singular giant wasp might be four feet long.

Demesne

Like nature spirits, spirit beasts typically mainly desire to protect their demesne. But this encompasses its whole hunting ground or personal territory. It’s partly sustained by the psychic energy it gets from creatures in its demesne, particularly those who revere, worship, or fear it, so it doesn’t require huge amounts of food.

Unlike a nature spirit, the physical body the spirit inhabits can be killed, destroying them; silver or magical weapons are necessary. But, as living creatures, they are not subject to a cleric’s banishment. Being more intelligent than mundane beasts, they may take up a cause or unfinished business related to their home, and satisfying that cause may give them solace.

Altho hostile ones may be termed “demon bear” or “devil wolf” or some such, they are not, strictly speaking, fiends.

Examples

1. The Demon Bear of the Northwood

Brutal god of the Thrazo barbarians, Kinto is a brown bear of incredible size. He participates in raids and carries the barbarian chief into battle and in grand processions. But Kinto can be vicious to his own people if they fail or otherwise displease him and has been known to devour a leader before the astonished eyes of the gathered tribe.

2. The Giant Bees of Cartum

The Temple of Cartum was left unfinished when it was abandoned as a result of a massacre by bugbears. When the bugbears moved on, the survivors returned from time to time to lament their losses and failings. A tremendous storm brought a nature spirit to the place and bound it to a hive of bees. The queen grew to enormous size and brooded a colony of giant drones and worker bees to attend her.

The hive took up the cause of the former inhabitants and gathered stone and other materials to complete the temple in their own strange fashion, filling it with their honeycombs dripping with magical honey and protecting themselves with basic traps. They are effectively worshiped by some locals.

3. Zidaza, Giant Tigress of Torvamir

Torvamir the Elven Warrior found great companionship in Zidaza, a giant tigress from the southern Fetiti Jungle that strikes fear into the hearts of his enemies. The foreigner is legend among adventurers, riding Zidaza on a custom-made saddle and wielding dual axes.

4. The Drovin Beetles

A pair of giant beetles cause much trouble along the Drovin Ditch in the borderlands by tunneling all thru it. Many creatures have taken up residence in their tunnels, and the common folk of the area are at their wits’ end to stop them—altho some actually revere them.

5. The Eagle Roltir

Roltir is a giant eagle that has protected the elven forest of Arvelda for decades. He is particular friends with Sinkara the druid and Verhold the ranger, altho those two do not get along themselves. (Some blame a lovers’ quarrel.)

Altho Roltir can speak some words, he principally delivers the messages of others by scroll.

6. The Black Wolf of Anschul

A great black wolf has menaced the city of Anschul for years, taking lone peasants and livestock as prey. Locals feared a werewolf, but a band of folk heroes, the Goodfellow Adventurers, fought it in its lair with silver spears. Altho they failed to slay it, they found it keeps the bones of its victims in piles, with one pile being entirely skulls.

7. The Crow Brothers of Gaverbor

Three hooded crows the size of small children roam the city of Gaverbor. They are brothers out of a nest in the city’s bell tower. Their giant mother was killed for cutting the bell rope and sending it crashing into the ground floor, but the brothers lived and became characters in the daily lives of the citizens. All three speak wisely.

Corbin favors the homes of the town council members and likes to repeat their grave pronouncements around town; many get their news from him. Theon prefers the local church and sings songs of praise and sometimes “marries” random couples in the street. Doric lives as the companion of Hovert the Sage and has become surprisingly knowledgeable.

8. The Demon Boar of Krykolwood

Krykol, on the wild borderlands, had its pleasant woodland invaded by a terror of a boar that knows no fear. It chases and sometimes kills all who cross its path. It ostensibly guards a dark witch’s grotto around a pool, and she tends its wounds when it is attacked. The paladin Sir Ansaius caught the witch unawares when the boar was lured away by others. But he became entranced by her and remains her captive.

9. Magala the Behemoth

Magala is the revered companion of the itinerant nun (monk errant) Oyo. A gigantic tortoise, Magala is thought to have lived with several nuns over several hundred years, but Oyo travels extensively and introduces Magala to many people across the several realms of the known world. Magala is said to speak, but only to Oyo.

10. The Great Rats Under Freeport

A mother rat inspired by a nature spirit birthed a litter of several offspring of great size that inhabit the cellars near the docks of the city of Freeport. They cause a great deal of consternation, digging extensive tunnels, stealing goods from the docks, and befriending a host of mundane rats.

11. The Green Stag Mirakin

The ranger Berin freed a great green stag from a cluster of brambles it had got its antlers stuck in, and they became fast friends. Mirakin, as the stag came to be called, protects the forest and alerts Berin and others of intruders. Mirakin is particularly known for “trooping the ridge” at midnight on patrol and has sometimes borne Berin on his back like a steed.

12. The Dread Serpent of Incaris

The ruins of a mountain pass fortress, Incaris, became the home of a huge snake, Vivicala, which hoarded goods captured from smugglers who dared attempt to cross the Frozen Border Ridge. A band of barbarians, Brothers of Blood, killed her with great losses of their own and found her body and venom to be of far more value to apothecaries and alchemists than anything she hoarded.

When the barbarians returned to search further, they found Vivicala’s nest, which had hatched a brood. Few of them survived to tell of it. All but one of the spawn of Vivicala escaped to take up residence elsewhere, and the legend gave rise to an evil cult in the ruins.