Companion Set

The Companion Set, or Companion Rules, are the high-level rules in the Tom Moldvay spinoff of the original Not-Advanced D&D rules. They kick in where the Expert rules taper off, 15th level by the charts but read-ahead parties might consider 9th in parts. Frank Mentzer, after a thorough retcon of Basic and Expert, put this out around 1983ish.

This Set's targeted levels overlap high-level AD&D, so the core content presents 1970s-era mainstays to 1980s-era players. At 15th level come the seventh and eighth level tiers of spellcasting, where mages really start to kick some ass. And - finally - the party will meet the Ghost and the Beholder. (Tho' not yet the Lich. Nor any demons despite the teasing of Planes.) Also here are some high-ish difficulty monsters mooted out and about in the Expert line, like X5's malfera.

We do have to hit the editors for klutzing up the alphabetic order of the monsters however, including - laughably - the gremlin. And the undead here are overstuffed: we didn't ask for a Phantom / Haunt division of six (6) all-incorporeal undead, and the Spirit takes the L for including the Revenant which, honestly, should be its own (dangerous) thing. The AD&D crew realised this so you won't be seeing this shite in future editions.

The player-characters and their enemies got some new weapons, like the bastard sword that can be used onehanded or twohanded to kill Kenny. Also the blackjack / sap for the Thief (mostly) to knock out an unhelmeted sentry; and the bola, to trip up foes from a distance.

Also brought to the table are proto-Prestige classes, basically. Your Lawful Fighter can be a Paladin, your Chaotic Fighter a sort of anti-paladin named an Avenger, Neutral Cleric a Druid, etc.

Also also here: some way for the Elf and other demihumans to keep progressing along with the humans - by way of alphabet-levels, in lieu of numeric-levels. And the demihumans each get a MacGuffin artifact to form the core of their lairs: Tree of Life, Forge of Power, and (for the wee folk) the Crucible of Blackflame. Again... not every idea here is perfect.

The DMs' book includes two "mini adventures" that are little more than single-combat setpieces. One is a tournament featuring a knight named Sir Guy de Gax; the other, a pit-fighting arena that forbids spellcasting. Recommend inviting Statler and Waldorf to both.

At 15th level on up, really 9th on up, the PCs should be considering doing a Conan and ruling domains of their own, delegating other - lowlevel - adventurers to do grunt work like goblin hunting. There are some brilliant ideas in the Companion DM section on what PCs can do in the meantime; most salient, that domain-ruling mechanic (better keep that Confidence Level high, folks!) and also the WAAAGH Machine, sort of a "Take Two" for old Chainmail. Although the 'Machine was somewhat Strategic for tactical tabletop gamers' tastes, so BATTLESYSTEM would serve that latter niche.

Beyond 24th level, PCs would be moving on from Mature to Epic, so the Master's rules kick in after that.

The modules in this system began CM-. Some of them are good, although it all starts out as a bare showcase for the system.

Overall, the Companion Rules were awesome, or at least formed a serious competitor for high-level AD&D. Their Set both scaled better than AD&D 1e and provided some large-scale heroics for parties beyond just bashing skulls.