Creating a Tentacle Monster

[werescythe]

So the idea is that this character was transformed by some magic mishap and now they are a tentacle monster. The concept is that when they fight and stuff they will use their tentacles exclusively (for the most part).

I'm currently thinking Simic Hybrid (with grappling appendages being some of the tentacles), however I'm not too sure what class/subclass to go with or what feats could really work with this.

Perhaps either Beast or Wild Magic Barb, though there could be other potentially interesting options for a class or feats. Please feel free to offer your suggestions on how to expand upon this idea/concept.

[Sparky McDibben]

This might be a fun idea for a Str-based monk (although quite MAD) that gets a lot of damage from picking up enemies and slamming them into hard surfaces or just chucking them.

[JoeJ]

Thematically, a warlock of either the GOO or the Fathomless is probably the best fit

[Greywander]

A couple of things to note real quick: First, your grappling appendages are natural weapons, which I think means you can smite with them, so paladin should be viable. They are not, however, finesse weapons, so rogue is probably a bad choice.

Rune Knight fighters make excellent grapplers, moreso because of their size increase ability (up to huge at 18th level!). You don't really need the unarmed fighting style since the grappling appendages already deal 1d6 damage, however, I can't really think of a good fighting style that fits the concept (Defense is the optimized choice). Maybe blind fighting? With four limbs, you may very well want to go straight fighter for all four attacks (allowing you to grapple a creature in each hand).

The rub with fighters is the armor, which is difficult to fit into the concept of a tentacle monster. Barbarian can be a viable alternative, with Rage giving you advantage on your grapple checks. Possibly less optimized, though it depends which subclass and what you do with it. Bear Totem is a solid grappling option, since grapplers are more concerned with staying alive than dealing lots of damage.

If you're less interested in grappling, I think some variety of monk would be a good option (they're specifically built for unarmed strikes). As with the barbarian, you can eschew armor, and you also get to jet around at lightning speeds smacking people with your tentacles using your martial arts die. Stunning Strike is also on point for a creature so horrible that it stuns people just by touching them. If you can pick up Athletics expertise, then even with poor STR you can still occasionally grapple if you want.

Are you interested in caster builds? It sounds like you want to use your tentacles, which a caster wouldn't really do. Perhaps some kind of gish?

[Quietus]

Always an option : Astral Self monk. Your first turn is spent manifesting the tentacles (read : releasing the kraken), slapping everyone around them, and since it's an action that cost ki, you can slap one guy an extra time. And then on the following turns, go to town with your reach-having tentacle absurdity.

For extra reach and ganglyness, use bugbear and reflavor long arms as tentacles.

Even when you're not using the monk-granted tentacle nonsense, you can still just flavor that your unarmed strikes are tentacle slaps.