Shulk 101
Monado Art Landing Lag Cancel
Monado Art Landing Lag Cancel, or MALLC is one of Shulk's most fundamental techniques in high-level play. It uses a unique property of the Monado Art activation poses that allows Shulk to act almost immediately out of many actions-- primarily, when he should be undergoing landing lag. The Art Activation Pose interrupts the landing lag, allowing you to act with any move after only 6 frames (the FAF of the activation pose). In addition, during the first 14 frames of the art activation (including the 6 before the FAF) Shulk is intangible, thus meaning that any of your opponent's move (i.e. an attack or grab) will whiff entirely, with no hitlag or hitstun on either character.
The possible applications for MALLC are nearly endless, but there are three main ways to look at the technique: 
1. Creating safe pressure
This is the most basic function of MALLC, as you are capable of using aerials that would otherwise be unsafe on shield by maintaining frame advantage vs your opponent. Although Shulk does not have many fast offensive moves to contest speedy opponents, he can act either offensively (i.e. grabbing or attacking) or defensively (i.e running away, jumping away, countering) after a successful MALLC. A very strong mix-up option is to abuse the full 14 intangibility frames of art activation by doing nothing; if an opponent attempts to Shield grab or attack you during this time, you will be able to easily punish their whiff with a grab or attack of your own.
Using the iFrames of art activation to avoid Mario's fsmash. 
2. Extending combos or strings
This has an incredible amount of depth to it, and so will not be covered in extensive detail here. As a rule, MALLC can be used to extend small points of advantage for Shulk, allowing for him to cover multiple options and create frame-trap situations. 



Speed Art Buffer Deactivation out of a dthrow into Jump Art MALLC fair

3. Escaping your opponent's pressure / strings / frame traps
This option is particularly powerful due to the fact that Shulk can activate and de-activate arts while in hitstun. While in a string, shuffling to an art and MALLC airdodging can allow you to escape without fear of your air dodge going punished by your opponent. This also means that Shulk can safely avoid strings that are usually meant to frame trap opponents after an air dodge. 
This also applies to juggles; MALLC air dodge or MALLC aerial is a very helpful tool in avoiding juggles, allowing Shulk to return to the ground safely despite the slow start-up on most of his aerials.
A MALLC airdodge from the ledge to escape Robin's pressure.
MALLC Timings
An important factor to consider about MALLC is the difference in timings between a MALLC on hit, and a MALLC on whiff / shield. 
In the above example, P1 and P2 both execute a frame-perfect MALLC. However, P2 lands on the ground slightly later due to suffering hitlag from hitting P4's shield, but the art activation is delayed by the same amount as the hitlag. P3, on the other hand, lands on the ground as the same time as P2, but without his art activation delayed, thus missing his MALLC entirely.
This means, MALLC on Shield and on-whiff have identical timings, while MALLC on-hit must be done earlier (a fast-fall can compensate). 
Practice Drills

Video Tutorials