Combining two runes will give you a random rune of the same tier. Combining 5 runes will give you a random rune of the next highest tier. You cannot combine 5 tier 3 runes at once (as there is no tier 4).
The rune combiner is random. It doesn't matter whether you combine marks, glyphs, seals, or quintessences -- they all work with each other, and the output can be anything.
The idea is that, generally, runes themselves are priced such that it is slightly cheaper to generate a tier 3 runeset from your old runes than by buying the tier 3 runes on their own. For instance, the level 1 +AD rune is 15 ip, while the level 2 +AD rune is 80 ip -- if you bought 5 of the level 1 runes, combined them, and wound up with a level 2 +AD rune, you would have saved yourself IP.
Unfortunately, as mentioned earlier, this process is completely random. If you have tier 1 and 2 runes, by all means, combine them to higher levels; the rune combiner is just a way to possibly recoup the IP you spent on runes you no longer find useful, but it cannot be counted on to give you what you want. You might luck out and combine 2 random runes into a +Dodge quintessence (very expensive!) -- or you might get a mana/5 Mark (with a tertiary stat, and probably not worth the IP cost of your combined runes).
It's very much a gamble, and you don't get anything exclusive from it, so use it if you need to get rid of T1 / T2 runes, and safely ignore it otherwise.
Tenacity is a mechanic that reduces the duration of crowd control
effects. It does not affect the potency/strength of the effect.
Tenacity works on: Blind, Forced Actions (Charm, Fear and Taunt), Pacify, Silence, Snare, Slow and Stun.
Tenacity does not work on: Airborne (Knockback, Knockup and Pull) and Suppression.
Contrary to Deotronic's answer, Tenacity does not reduce the amount of slow. It only reduces the duration of the any of the CC that is affected by Tenacity. The reduction is reduced by a percentage equal to the Tenacity value. So a champion with 35 Tenacity will have all affected CC reduced by 35% duration.
EDITED to reflect changes to Season 3 tenacity items:
Please note that Tenacity does not stack. There are currently 3 items which provide Tenacity, and they all give 35 Tenacity. If you buy two of these items, you will not get 70 tenacity. You will only benefit from 35.
- Mercury Treads
- Spirit of the Ancient Golem
- Zephyr
Source
Best Answer
In League of Legends, there are seperate Elo scores for each gamemode's matchmaking. This means that your ranked Elo is seperate to your standard (normal game) Elo.
When going into Matchmaking, the matchmaking system uses the Elo that corresponds to the gamemode you're queuing for.
Because Ranked games and standard games are considered two different gamemodes, they have two different scores.
(ie. You have 1000 Elo (it's an estimate, we don't actually get to see this value) in standard games, and 3000 Elo (this value is visable in your Ranked stats) for ranked games on Summoner's Rift. This means that your next standard game will be against those that have a lower skill-level than you, while your next ranked game will be against those that are the same skill-level as you.)
As far as the matchmaking system is concerned: Your ranked Elo (MMR) does not affect the standard Elo (isn't taken into consideration during Standard Game matchmaking).
The point is: Even if you're the top player in Ranked games, and you've never played a single standard game (not possible, since you HAVE to play Standard Games to be able to level up), you will be matched with those close to the starting Elo if you were to play a Standard non-ranked match. The matchmaking system does NOT care about your ranked stats (MMR, Elo, etc.) if you queue for a Standard non-ranked game.
The only thing that will be taken into consideration is your loading screen portrait, which reflects the current league you're in.