Thunder Pegasus
Very Rare Purple (or Crazy Rare Dark Blue) recolour of Flame Pegasus.
Picture provided by @4d_fury
Weight: 5.3g
Unique rounded edges and an edge-focussed weight distribution are good for stamina, the former helping compensate slightly for the fact it is wider than Wide Survivor.
The rounded edges provide some ability to destabilise opponents, providing some versatility both on low combinations as well as Force Smash combinations, but advantage from this is negated by its greater recoil in both Left- and Right-Spin than alternatives such as Tiger Defenser, and for Force Smash, its range tends to be too short compared to Smash Turtle (though it is somewhat usable here).
Right Spin:
Slopes provide moderate upper attack and contact points provide moderate smash as well as a little recoil.
While usable for Compacts in this direction, the rotational recoil from the contact point shape and width of the AR means it is less effective than top tier ARs such as Tiger Defenser as the recoil causes it to fail to outspin a lot of key opponents including other compacts for a minimal offensive improvement.
Being slightly wider than Wide Survivor is an issue for use in Survival and Defense customizations as it has more recoil than smaller alternatives, relegating it to tier 2.
Can be used for Force Smash, but it is not wide enough to be truly effective like Smash Turtle, and has somewhat too much recoil for effective use.
Some use for Spin Stealing Attack however it lacks the offensive power to really make a combo more useful than just a regular Spin Stealer.
Left Spin:
Higher recoil than right spin as the contact points are the spikes at the front of the wings.
More offensively capable but still not terribly powerful.
Overall worse than right spin due to inferior defensive ability.
Still usable for compacts and to some degree Force Smash, but not particularly good in this direction.
Weight Disk: N/A
Gyro Engine Gear and Engine Stopper Base do not fit a Weight Disk. The metal disk of Gyro Engine Gear provides the bulk of the Beyblade's weight instead.
Weight: 21.2g (including 2x stock plastic bearings weighing 0.04g each)
Must be used with Engine Stopper Base which doesn't support a WD, meaning the fact it is technically the heaviest Spin Gear is mere trivia.
Main EG gimmick is a bearing-mounted gyro section with CEW support which connects to the AR and Engine Stopper Base only via the two bearings.
Both bearings are legally interchangeable with others, however the top can have fitment issues with some molds of the casings and certain variations, and the bottom one requires some force to access, either removing the prongs or the spacer. If removing the spacer, one should be careful to put it back in the same position (generally by marking the shaft) to ensure stable usage.
In this mode, Gyro Engine Gear can be launched by pushing a ripcord through the base on either side for left and right spin - this makes it technically the first Dual Spin Beyblade and therefore perhaps the progenitor of the HMS series, Gravity Perseus, and Variares. It is also the only way to legally use Four Layer System ARs such as Roller Defense Ring in Left Spin.
Other gimmick is a switch that holds the gyro part in place, allowing the Beyblade to be launched as usual. This has no competitive use.
Interestingly, it is generally best used with its stock CEW, Metal Sharp which provides by far the most controlled behaviour while also being relatively short - important for retaining stability, the largest challenge the part faces.
The various gimmicks make Gyro Engine Gear a ruling nightmare with multiple legal ways to launch and specific rulings required for operation. I will quote directly from the rules below:
Gyro Engine Gear may be legally launched in one of three ways:
If using only a launcher, the Beyblade is to be launched in line with standard launch protocol.
If only using the Engine Gear to launch without a launcher, you must place the Beyblade at the Tornado Ridge of the BeyStadium. If the BeyStadium does not have a Tornado Ridge, you must place it approximately 3cm from the edge of the BeyStadium wall. In this case, you must be sure to release the Beyblade from your hand onto the BeyStadium floor during the word “shoot! with the tip of the CEW making first contact with the floor of the BeyStadium.
If using both the Engine Gear and a launcher, the Engine Gear must be spun during the countdown, and the Beyblade launched from the launcher during the word "shoot!" as normal.
When replacing both bearings with Shielded Ball Bearings, Gyro Engine Gear goes from a fun gimmick part to one of the scariest stamina types on the game, ominously T-Posing over the competition as they flag and die.
This is due to the main spinning mass of the Beyblade, the EG "Weight Disk" part and CEW (upon which determination of whether the Beyblade is spinning or not is based - the AR and Engine Stopper Base are ignored) being isolated from opponents by the free spinning bearings, meaning they are unable to wear it down or steal spin from it (due to the outer shell having minimal momentum of its own), combined with its dual spin nature meaning it can opt for the marginally better match up dependent on the opponent it faces.
This does require the use of a small set of defensive Attack Rings, and in particular its properties can be further capitalised on with the use of free-spinning Sub-Rings such as Dragon Saucer and War Monkey SARs - though in an odd twist, War Lion's SAR tends to be too small to work while Dragon Breaker SAR gets its closest to Competitive relevance here by being mostly okay, if a little weak defensively to contend with more conservative choices.
As such, it is very challenging to outspin without very significant destabilisation and even that is hit and miss.
However, it is very susceptible to Knock-Outs, even Balance types such as Force Smash Combinations and some compacts have the ability to send it reeling potentially out of the stadium.
Overall, this "joke" part has suddenly found itself near the top of the competitive pile and the subject of a very lengthy ruling clarification section.
Weight: 5.5g
Must be used with Gyro Engine Gear.
Despite its name, the actual Engine Stop gimmick is part of Gyro Engine Gear, Engine Stopper Base is simply a plastic shell which houses Gyro Engine Gear to prevent damage etc.
Has two sloped protrusions which have relatively minor interaction with opponents as they tilt due to the generally free spinning nature of the part in its primary mode of usage, though they can provide some destabilisation.
There is a minor mold variation where some versions lack the small line near the ripcord on one side.
Weight: 3.3g
Flat surface with a small metal point in the centre.
Tip has some precession, however for use with Right Customize Gear (Free Shaft Version) it is outclassed by Light Sharp, which has excellent precession and allows for actual Zombie customizations (albeit right-spin only).
However, Metal Sharp ends up being more notable due to chemistry with Gyro Engine Gear, providing surprisingly excellent stability due to the low height, somewhat ball-shaped tip, and bevelled surrounds combined with the bearing support offered by the part reducing the impact opponents can have on its stability. As such, it ends up being arguably the best true CEW competitively.
Overall
Thunder Pegasus and its sibling Flame Pegasus were previously considered Beyblades intended for fun (and in the case of Thunder, collection) but thanks to the unique and exceptional Gyro Engine Gear, it is now a very serious competitive blade. However, Thunder Pegasus itself commands an incredibly high price (even before considering the Dark Blue version), even Capricorn Strike G is somehow more affordable than Thunder Pegasus (and has a more competitive Attack Ring), with Flame Pegasus being the sensible choice of the three. Thunder Pegasus is best left to collectors.