Dawn and Dusk Digimons unveiled
Apollomon, Dianamon, and GraceNovamon are finally unveiled in this set. This digivolution line has a new mechanic that takes the top card of the Digimon's stack and puts it at its bottom digivolution card to gain some memory or de-digivolves for cheap/free. In a way, this sounds like a re-digivolving process (removing the current LV.X Digimon and re-digivolves into another LV.X Digimon) so we shall call it "re-digivolve" for simplicity.
Essentially, re-digivolving allows the player to not only abuse their Digimon's [When Digivolved] effect, but also cycle their cards in hand. However, the effectiveness of this ability in competitive play remains uncertain. The LV3 rookies Coronamon and Lunamon, as well as the red tamer Koh and Sayo, grant this re-digivolve effect.
The red Coronamon/Apollomon line emphases offence. The LV5 Flaremon has a [On Play]/[When Digivolved] effect that deletes your opponent's Digimon with 5000 DP or lower, while the LV6 Apollomon can ideally delete your opponent's 16000 DP Digimon, with [Blitz] and 2 checks to boot.
The blue Lunamon/Dianamon line emphases defense. Both the LV5 Crescemon and LV6 Dianamon has the unique ability that prevents your opponent's Digimon from suspending (hence cannot attack or activate effects by suspending, which are especially rampant in green).`
At LV7, GraceNovamon can be DNA digivolved from Apollomon and Dianamon at 0-cost for board control, [SA+1] and [Blocker]. But the most interest effect being that he can be very difficult to remove from play.
The blue tamer Sayo & Koh is the secret sauce that allows you efficiently digivolve into GraceNovamon.
Devas, Four Sovereigns, and the God Beast Huanglongmon
After almost 20 sets, Bandai finally unveils the much awaited Fanglongmon (or Huanglongmon).
In EX-5, the four sovereigns are redesigned as ACE cards, and plays with a huge variety of Deva Digimons cards in a unique mechanic. Devas are usually LV5 Digimons that has a unique effect that lets you play another Deva for free into your Breeding Area, so the game plan revolves around playing LV5 Digimons and ACE digivolving into LV6 sovereigns.
The game plan in this deck is to slowly mill and have some board control with your Devas and Sovereigns, and then launch Fanglongmon for further board pressure and for the win. However this deck may give away a lot of memory in the process so it is interesting to see how this mechanic fares competitively.
Lots of Leomon
Many of EX-5's Leomons possess the new [Indomitable] effect, giving them a lot more board protection in today's meta landscape.
The new LV6 HeavyLeomon has high versatility aggression, armed with an arsenal of effects such as [De-Digivolve], return to deck bottom, and unsuspend, while the new LV6 BanchoLeomon is more defensive. Both cards, together with their new LV5 lines, will be welcomed additions to many Leomon decks.
New support for Etemon
Bandai has tried for the past few sets to buff up the iconic Etemon, but this Digimon line has never managed to pull in the spotlight in competitive scene. We believe that this will change in EX-5, with the new LV6 MetalEtemon having immensely powerful board control effects.
Aside from a good Digimon/Tamer deletion effect, MetalEtemon can also recover and manipulate your security stack, and reroute attack target to himself or your security. This effect synergies very well with BT14 Etemon as well as the Suka's Curse option card.
New X-Antibody
With the old BT9 X-Antibody being a little obsolete, a new X-Antibody option card is now included in EX-5. X-Antibody Protoform not only reduces digivolution cost, but most importantly grants your Digimon some much needed board protection. We should see a lot of this card in upcoming decks, and there seems to be a silent synergy with the Magnamon line.
Other notable Digimons
Metalgarurumon X-Antibody is a surprise re-introduction in this set, and has very good balance of offence and defence. This card will serve as a good entree before BT-15 reveals a whole new line of Garurumons. An alternate vintage card design is also included for this card (not sure if it's a high rarity pull).
Mitamamon is a new LV6 yellow Digimon that has a versatile set of offensive/defensive effects. He should work very well with BT6 Mimicmon and BT4 Lucemon.
Merukimon is a new LV6 green Digimon that synergises with the new [Indomitable] effect, but since this is only the first set where this effect is introduced, Merukimon may not see a strong scene yet in decks.
Anubismon is re-introduced in this set having immense synergy with many existing cards/decks. Being able to play any purple Digimon from trash with heavily reduced play cost, makes many hard-play Digimons (especially those with [Digixros]) such as Mervamon and Bagramon/Darkness very playable.
Leviamon is also a much awaited Digimon, being one of the few Seven Demon Lords that has yet to be unveiled. At LV6, he has the ability to delete 2 of your opponent's Digimon, and gains memory for every of your opponent's Digimon deleted (similar to BT3 Malomyotismon).
Summary
In summary, EX-5 unveils a new effect [Indomitable], some new play mechanics coming from the Dawn/Dusk Digimon lines and Sovereigns lines, and subtle buffs to a number of decks through singular (mostly LV6) cards.
I felt that the set can be a little better (many other animal/beast Digimons that can get a buff) and there is an unnecessary 12 slots wasted for Deva cards (much like EX2's Mother Reaper line). But otherwise, there are enough cards in this set to encourage creative deck building!