Following a smaller update in the form of patch 3.20, Hi-Rez Studios has detailed Smite's 3.21 patch, which features a more substantial addition in the form of a new character.
Thoth is a Mage whose mechanics largely center around the book he carries. Killing any enemy, including minions, adds their name to the book. For every 30 names, he gains a stack of five magical penetration, ultimately earning up to as many as five stacks once he reaches level 17.
The Glyph of Pain ability is also central to how he plays. This creates a hieroglyph in front of him, and any abilities of his that pass through it receive a range and damage increase. Basic attacks fired by him or his allies through it get a smaller damage bonus, but they don't travel any further than they normally would.
That glyph can be used in conjunction with Thoth's other three abilities. Hieroglyphic Assault drops the basic attack movement penalty and causes his next three basic attacks to pass through enemies and do ability damage. Ponderous Escape lets him dash in the direction he's moving and then fire a projectile that slows and deals damage.
Thoth's Ultimate, Final Judgment, summons pages from his book over a short period of time. When four have been summoned, they shoot forward, dealing a large amount of damage to all enemies in their way. This can be activated early to shoot fewer pages, but this comes at the cost of dealing less damage.
Update 3.21 also introduces several new skins for other characters, some of which are quite good. Ymir's Baron Frostchild outfit gives him a top hat and suit, while Igneous Terra turns her into a cross between her usual look and that of Agni. There's also High Noon Sylvanus, which dresses him up in some wild west attire and gives his tree the look of a cactus. Finally, Hades' Heebee Chibi skin makes him look downright adorable.
The remainder of the update deals primarily with balance changes. Item changes are fairly limited: Spirit Robe's passive now has a 15 second cooldown (up from 10), and Oni Hunter's Garb now provides more crowd-control reduction and fewer protections from its passive (but those protections are granted more frequently).
On the character side, Terra's Monolith can now be destroyed by three basic attacks. Chiron sees a boost to the speed of his Centaurus arrows and a cooldown reduction on Training Exercise, allowing it to be more frequently used offensively and defensively (it can cleanse allies in addition to doing damage). Erlang Shen's Pin now Roots for a fixed amount of time at all levels (1.3 seconds, which is down from where it was at max level), and the same is true of Freya's Banish (1.5 seconds, but it now costs less mana).
Kukulkan's Slipstream now provides more movement speed initially, but the effect lessens over time. Some of the recent changes to Susano are undone, as his Ultimate knocks up enemies after one second (indicated by a visual cue) and there's less of a wait before the first hit of Storm Kata. Mana costs for two of Xbalanque's abilities are lowered, and Hou Yi's Ultimate causes an additional Slow on targets he has marked.
You can check out the full patch notes on Smite's website.