Note: This item was created for 5e D&D, so a lot of the dice and rules are specific for that game system. However, if you like the idea, feel free to modify it to fit your game.
"The town's still a few miles away yet," Hyla complained, shouldering her pack higher. "And these ogre heads are getting heavier by the minute."
"Just one second!" Tule cried, setting his pack down. "This is the perfect opportunity to use that ring I got from that wizard last week!"
"That grouch?" Hyla asked, setting her pack down as well. "I'm surprised he didn't turn you into a toad after you upset his cart like that."
"Nope, he sold me this ring," Tule gestured to an ornate silver hand on his hand. "He said I could use it to change into any horse of my choosing!"
"Well that's great," Hyla said sarcastically. "I didn't really need an adventuring partner, just a pack horse."
"It's not permanent, twig-brain. It only lasts as long as I want it to."
"In that case, get going! The sun will be setting soon."
"Fine," Tule said, giving the ring a twist. "One black stallion, coming up!"
A flash of light consumed the elf, and once Hyla's eyes had adjusted, she saw, to her surprise, a brown horse standing in his place.
"Black, Tule?" she quiried smugly. "Do you even know your colors?" When the horse only responded by cropping at the plains grass by Tule's abandoned pack, Hyla began to take the issue seriously.
"Tule? Hey, quit fooling around!" The horse ignored the protest, calmly continuing to graze.
"Ooh, when I get my hands on that wizard... your pride will be avenged, brother!" Hyla looked closer at the unresponsive horse, then gulped nervously. "I mean, sister."
This ring, created by a wizard with a vendetta, allows the user to take on any shape of one animal type using up one charge. The ring can hold three charges, and regains 1d4 - 1 charges every noon-hour. However, the ring is persnickety, and requires a strong mind to keep it in check. Upon the usage of the ring, a character must make three ability checks: An intelligence check with a DC of 10 to choose the specific form (e.g. brown horse, black wolfhound, white rat), a wisdom check with a DC of 15 to control duration, and a charisma check with a DC of 5 to maintain personality, mental scores, and alignment. If a character succeeds all these checks, he or she may shift into any shape of the ring’s type, with their specifications of physical details, for up to 8 hours, ending upon their wishes, and retains all mental stats and personality. If the character is a druid, he or she has advantage on these checks. Roll percentile dice and use the following tables if you should fail one or more of the checks. (Variant Rule: for added excitement, add the failure margin to the roll for the table. A fumble equates to a 100) Intelligence Fail: 1-20 Completely different appearance within bounds of ring 21-40 Similar appearance, 1-2 minor changes 41-70 Different color 71-95 Different breed or subspecies 96-100 Different species entirely, not necessarily even within bounds of ring Wisdom Fail: 1-20 Roll again on this chart for maximum duration, but the character may make a WIS save with a DC of 15 to shift back at any point 21-40 1d4 hours 41-60 1d6 hours 61-70 1d8 hours 71-80 1d12 hours 81-95 Roll again, doubling any result 96-100 Permanent, must be removed by remove curse or dispel magic, either cast as a 4th level spell or higher. Charisma Fail: 1-20 Gains only the alignment of the animal shifted into 21-40 Gains the wisdom of the animal shifted into 41-60 Gains the intelligence of the animal shifted into 61-70 Gains the charisma of the animal shifted into 71-80 Gains the personality of the animal shifted into 81-95 Roll twice on the table, using both results 96-100 Gains all mental stats, alignment, and personality of the animal shifted into, virtually indistinguishable from a regular animal.