This is a repost from Rampant Games After you're done here go check it out.
Roll 2d8 or Choose:
2 - Straightforward
3 - Ambush
4 - Exposition
5 - Tactical
6 - Avoidable
7 - Mixed
8 - Deceptive
9 - Programmed
10 - Hostile
11 - Booby Trapped
12 - Exceptional Enemies
13 - Waves of Enemies
14 - Weakened Enemies
15 - Non-Lethal Attacks
16 - Rule Changers
Straightforward combat encounters - Nothing much to write about here. But often these involved a new monster type or a spellcaster or "boss-level" enemy which the players won't be familiar with. Or the tactics the enemies used might be a little unusual to mix things up.
Ambush attacks - monsters attacking from hiding to get an initial advantage (but quickly devolves into being a straightforward combat). Certain monsters were simply made for this kind of attack - like trappers and lurkers above.
Exposition Encounters - These might be encounters that resemble types 1 or 2, but actually provide clues as to the bigger picture. For example, orcs that are visibly nervous about guarding the entrance to the graveyard, and will not flee there under any circumstances.
Tactical Challenges - these battles involve a significant tactical wrinkle - like fighting on a bridge over a lake of fire, or something as simple as the enemy taking advantage of cover or the high ground. Anti-magic fields are also popular here. Tucker's Kobolds drove players insane with these kinds of battles.
Avoidable combats - battles which smart players can avoid completely by using their brains instead of their swords. There were often varieties of monsters coming and going in those old dungeons, which necessitated some loose agreements between them. The players could often exploit this situation. Using the correct password, or simply bribing the bored ogres might be enough.
Mixed battles - With creatures of complimentary abilities, the classic example is to pair a powerful but easily killed magical enemy with a very tough "tank" to protect it.
Deceptive Battles - Like the ambush encounter, but there's something going on that makes the entire combat confusing and unclear. A canonical example is an illusion that disguises the true nature of the enemies, or adds additional illusionary attackers to the mix. Why is that cow breathing fire, again? Or a field of darkness within which the enemy can see, but the party cannot. Or maybe the party doesn't realize that the beautiful slumbering maiden they've just "rescued" is actually a vampire who is currently attacking with her charm power prior to unleashing her more direct and obvious attacks.
Programmed encounters - these are combat encounters that are directed or triggered by some sort of trap or puzzle. "Lady or the Tiger" situations or room-sized chessboard puzzles with golems as the enemy pieces might be examples of this kind of combat encounter.
Hostile Battlefields - This is a lot like Tactical Challenge battles (4), but there's an active environmental threat that makes time of the essence, or requires an active hand to avoid the threat as well as battle the enemies. An example might be a room with the walls closing in, or filling with water, or a battle taking place around an artifact that is hurling fireballs at random locations.
Booby Trap Battles - These encounters are semi-passive, happening only if the party digs around looking for treasure. Oozes, slimes, rot grubs, mimics, giant centipedes, and poisonous snakes worked well here.
Exceptional Enemies - These encounters involved an enemy more powerful than the players expect, due to nature, spells, or equipment. The Hobgoblin chieftain might fight as a bugbear, the zombies might be outfitted with chain mail and pole arms, the ogre might be wearing a ring of protection and drink a potion of haste before the battle, or the goblin might actually be a vampire. Third edition D&D really took this to the extreme, with plenty of options for advancing or otherwise beefing up "standard" enemies.
Waves of Opponents - Reinforcements are arriving. To avoid facing increasing odds, the party might have to expend a few more resources to eliminate the earlier waves quickly to avoid fighting an overwhelming force.
Weakened Enemies - The party may face a creature typically more powerful than they'd usually be able to take on, but has some advantage which - if they exploit - can grant them victory. A Hydra might be bound on a chain to an area, the ogre camp may be sleeping off a night of drunken revelry, or the dragon may be injured from another battle.
Non-Lethal Attacks - The enemy launches a quick raid set the party back (and gain treasure) rather than to kill them. It may be a quick robbery to deprive the party of equipment (or the functional equivalent via a Disenchanter or Rust Monster), or an attempt to lure / force the party into a trap, or simply to get them to waste spells, potions, and charges on magical items for an all-out battle that doesn't happen until later. Another example is an entirely illusionary encounter, which again may cost the party resources.
The Rule Changers - The wildly bizarre, constrained encounter that the Game Master might have a tough time rationalizing, but really turn combat on the ear. The most common of these would be combats where the party is stripped of all their gear, and must fight unarmed or with improvised weaponry. More extreme rules might be a conflict that must follow the rules of Rugby or something like that. While weird, they can be enormously amusing.
I omitted the following from the table as whilst this combat encounter type can be fun - it can often lead to massive derailing decision made by players. Its your call if you like that or not.
The No-Win Scenarios - Like #5, but this is a battle which - if pursued to the ultimate conclusion - is for all practical purposes unwinnable. The only way to win is - not to play. Or rather, to find the alternative means of defeating the enemy. Players (and Captain James T. Kirk) hate these, but usually only because they don't realize its danger until too late. Presented carefully, I believe it is still a valid and enjoyable encounter.
: If you need something to stock your combat encounters check out the Iconic classic D&D monsters I've converted here :